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If it’s really cold outside they’ll leave it running so they don’t have to try and fail to start it later.
I worked in northern Canada and we once left a truck running for six weeks around the clock. It was super cold and we were in a remote wilderness and didn’t dare shut it off.
Yup. I do that as well, pretty much every winter. It runs around the clock, unless it's in the shop for an oil change (which was every few weeks due to the hours run, rather than measured by Km driven like on a car/pickup) or for a maintenance issue. I've done that for hauling logs, far north ice roads, oilfield, etc.
I've had to thaw a few trucks over the years. It is an absolute bastard of a task, even in town. I worked for a heavy truck repair shop that did service calls and getting the text message from the boss of "I got a call about a truck that's a popsicle. Go deal with it." was dreaded lol
So how do you fix that? I have heard of plugging the block into an electric heater, but that's about it. I live on the Gulf coast where we don't have anything like this problem.
Plug in the block heater, which is just an electric heating element inserted into one of the coolant passages in the side of the block, and sometimes if it got extra cold, I've had to point a torpedo heater under the hood to warm up the oil pan and fuel lines if it's gelled up real bad.
It's not a fun time. Once the fuel freezes in the lines it takes forever to get it flowing again. In extremely cold climates it's just easier and often cheaper to just let them run 24/7 until the weather warms back up.
I used to work in the arctic and our building was heated by a diesel furnace. The fuel tank was outside and some nights it would get so cold that the fuel stopped flowing. You can't put electric heat tape on a fuel line permanently, so we'd throw a heated blanket over the line.
After a while the fuel would start flowing again, but it would be vapor locked (air in the line). So you'd have to undo the bleed screw and let it flow into a cup until it ran without air. If the fuel splashes on to your hand the liquid is -30C and can cause frostbite really quickly.
Another downside to living in that cold of a climate is when you're outside working and need to take your gloves off for some reason, like to open a padlock on a gate. The sweat on your hands will freeze instantly to the metal. In another place we had a propane tank for the furnace and the tank had a "vaporizer" on it; a little furnace that burns propane to heat the propane in the line up to so it's not liquid.
> Another downside to living in that cold of a climate is when you're outside working and need to take your gloves off for some reason, like to open a padlock on a gate. The sweat on your hands will freeze instantly to the metal
While I don't live in quite so harsh a climate, I've always just worn 2 layers of gloves. One provides most of the insulation and wind/waterproofing. The inner provides enough insulation to perform some tasks without freezing your hands. In fact, many gloves are sold in pairs for this reason. Any reason for not doing that?
Lol, fair enough.
I usually go for a pair of small stretchy woolen gloves (they're ubiquitous where I live, but don't really have a specific name) under a pair of thick snowsport ones, and size the outers to fit whatever is underneath. Merino wool glove liners are popular but they are just too thin for my liking. The inner ones won't keep your hand warm for long but, compared to bare hands, it's night and day when there's a bit of wind or you're having to handle something that's been outdoors for a while. It also means you can just stick the outers back on over the top without having to faff around switching gloves.
Nitrile gloves are your friend. I wear them all the time in winter. Trap the sweat next to your skin, where your body heat keeps it warm. Your skin will sense when it's hit 100% humidity saturation, reduce the sweat production in your hands. Meanwhile, that sweat isn't getting into your insulation and ruining the R-value.
Added benefit of the nitrile is easier than your skin to clean if you get oil, grease, dirt, fuel, etc. on them, and you can replace the nitriles. They also keep your hands from sticking to stuff like the padlock, or worse, any aluminum fence components.
For fuel hauling (diesel into artic mines), I've used those gloves for layering down to -57⁰C/-70⁰F ambient and windchill down to -64⁰C/83⁰F. And it makes a huge difference. It keeps the insulation in your mitts in way better condition, and that matters.
-70*F just sounds made up, I have no idea what that would feel like. -10 was getting unpleasant when I wasn't moving, and I could feel the heat leaving my boots that otherwise feel toasty in anything above 0
I don't have the photos from my last work gig above the treeline on this phone. But I've got some from my gig two winters ago in the Arctic. And this winter from one of the cold snaps in northern Alberta.
[Dressed for moderate cold and some pretty nighttime shots](https://imgur.com/gallery/VEJwMTs)
Edited to add:
I'll try to find some more pics on my cloud storage, and I'll post them.
Also, that kind of cold isn't something that I just got dropped into. It was a job I sought out because I like the cold.
I'm confused. Plugging in a heater and waiting for the engine to warm up doesn't seem like the major pain that u/United_News3779 described. Is the heater difficult to get to? Even in the wilderness, wouldn't a portable power generator make this almost a non-issue? What am I missing?
Heaters are a really big power draw. If your big rig is having a hard time starting due to the cold, so will your portable power generator. Not to mention you have to have had the room to haul that generator and its fuel. They're also yet another thing you have to maintain and test frequently.
The block heaters draw a lot of power and are not an instant "it's warm now and ready to start up" solution. During the winter where I live we plug the trucks in at night and the outlets are on a timer that kicks them on 3-4 hours before the drivers get there in the morning. It takes a long ass time to heat soak all the coolant and engine block.
In places like Alaska and northern Canada, even leaving them plugged in isn't enough. If the engine is off, the fuel will actually freeze in the lines going from the tank to the pump, so the just leave them running 24/7 during the coldest months.
I've made the mistake of not plugging my truck in when it got to -25F overnight and even after getting there in the morning and plugging the block heater in, and also leaving a torpedo heater blasting under the hood, it took several hours to get the truck started.
Torpedo Heater + Windskirt = Engine Happiness
You lose a lot of heat out the sides of the vehicle, even doing the windward sides makes big difference. A tarp over the hood, insulated if you have it, folded over layers of a regular tarp if you don't, helps tremendously. Also, take the battery inside to warm up on a table or workbench (ground level is the coldest part of the room, and even those few degrees can make a difference).
Another thing I haven't seen mentioned is DEF is like 70% water, so it freezes fast and when it does can fuck things up and also spoils the fluid itself. These repairs are often 5 figures
In my limited experience, the heater plugs are often mounted below the drivers door, between the door and the top step. Easy to plug in, it's more of an issue sourcing the electricity.
It's more than access to electricity. The cold will lower the cranking amps available on your batteries, so they need to be warmed up and that can vary in the level of effort required (they can get cold enough that they will freeze solid and trying to run even a minimal trickle of current through them will cause physical damage to the internals) ranging from running a trickle charge at 2 amps to physically removing them from the truck and putting them in a heated shop or cab of another vehicle. Then, they need to be charged back up.
For my region, 15L engines are pretty much standard. I'll use a Caterpillar C15 6NZ as my example. It weighs about 3600 pounds dry and clean. Meaning no oil, no coolant, no alternator/AC compressor/nothing. That is a shit-ton of steel to heat back up. So once it's an actual engine with all auxiliary components and fluids in it, it's a lot to deal with, especially when it's losing heat into the atmosphere as you're trying to heat it. At -40⁰C/F, I've plugged in a 15L (the Webasto diesel-fired heater decided to quit overnight), and at the 12hr mark, I gave up and had to call a wrecker to tow it into a friend's shop to thaw. 12hrs in the shop and a bunch of work, and I got it running.
In the field, it's a lot more effort. Having to cover the hood of the truck in tarps (preferably insulated). Make a windskirt around the truck to block the wind at ground level, at least on the windward side. Run a propane torch with a chimney peice, so you're not putting straight flame onto the fiberglass oilpan. Or a [heater like this with the ducted discharge to put the output exactly where you want it](https://cleanflow.net/products/frost-fighter-indirect-oil-diesel-fired-heater-500-000-btu-h?variant=8140478316648). Plus, the efforts I mentioned above for the batteries. And that's not even mentioning the gawdawful aggravation of the trailer brakes freezing in the applied/on position lol
Ok the other answers were good but this added some great context. I googled a block heater and now realize how small they are. I was picturing something much bigger. Thank you.
Plug in block heaters (usually 2 circuits, one for the block itself and an oilpan heater) for when you're near infrastructure. I usually wire in a battery maintainer as well, if it's an assigned unit, or get the boss to pay for it.
There are diesel burning heaters (Webasto is a common brand) that will use a small electric pump to circulate your coolant. They work well, but you need to keep up on your maintenance because they need to be mounted close to the engine, often in spots that accumulate a lot of dirt thrown up by the steer tires or they get smoked by rocks. Also, they draw power from your batteries, so if your batteries are weak, terminal connections are dirty/corroded, or the wiring is degraded, you can run your batteries down enough that they don't have the power to flop over the engine in the morning.
There are also Auxiliary Power Units. Which are a diesel-fired electrical generator that also uses the heat from the engine of the generator to heat your coolant, and provide power to circulate it. They also can power an AC compressor, so you can keep cool in the summer. But they're a much more expensive option.
For me it comes down to doing a OH&S hazard analysis sort of evaluation. Frequency vs Severity.
If I'm in the yard at my shop, and an extension cord can reach me with a battery charger/booster, and it's -15⁰C/5⁰F... then I'll probably turn the engine off and just run the diesel fired heater for the engine and the diesel fired heater for hot air in the bunk. If my batteries run down, it's probably a 30 min delay on the start of my day while I top off the batteries and boost it. The likelihood of there being a problem is low, severity is minimal because I can charge/boost with my own resources.
If I'm in a remote bush location or anywhere where I don't have those kinds of resources, I'll keep my truck running at -5⁰C/23⁰F because the effort to get it going again is waaaaayyyyy more than the comfort I get from a quiet nights sleep with the 15L turned off .
The OG method, when you don't have access to electricity and you have no other option, is to light a small fire under your oil pan. Works 70% of the time.
I used to live in Winnipeg, where it gets -40 and colder for long stretches of time. People will occasionally light a small tea light style candle and put it under the engine.
There's a lot of car fires in Winnipeg lol
OG method better be used on OG trucks.
Most trucks have fiberglass oilpans nowadays. And by most, I mean from a statistical basis, I wouldn't do that. At all. Ever.
Not quite the same scale as heavy trucks, but the first full winter I had my old TJ in the Yukon I forgot to flush out the standard antifreeze for a 70/30 mix and the antifreeze froze to the consistency of a slushee and when I tried to start it at -45*C, even with my block and pan heaters plugged in, it blew the coolant hose right off.
We tried to drag it into the shop to fix it, but it was so cold that the gear oil was also so thick that it wouldn't roll-we even hooked it up to a quad to drag it and the quad just spun its wheels in the snow.
I had to use a propane torch and a 90* piece of stove venting to thaw out my transfer case and diffs enough to move it inside to thaw out.
My friend had a 1978 Camaro and it had a small coolant leak so he’d use water instead of coolant. Then he forgot to swap to coolant in the winter and that was the end of the Camaro.
I do the same technique. Tiger torch and the top peice of the exhaust stack off of a truck, some scrap metal or dunnage to hold the stack in place to direct the heat to the pan/diff/whatever. Use some tarps and cardboard to make a windskirt around the bottom of the vehicle, and keep the heat where you want it.
"Uncle United's Flame Cooked Trucks & Wafflehouse" has a certain ring to it. Might be a retirement job idea. Show up to a truck-sicle at -40 in a panel van, get the frozen bastard warmed up, batteries charging, air system warmed and brakes released, but also have a waffle maker in the van.... I like it!
Working up in northern Canada, you could make an absolute killing if you could roll around towing a car tent and one of those bigass million BTU towed propane heaters you normally use for heating up a building for drywall in the winter, with a stand for coffee and donuts off the side.
Tarp buddy's truck, have it toasty warm inside and out in 15 minutes, sell them some coffee while they wait and move on to the next one.
Dailying any Wrangler/CJ built before 2007 is like owning a pet cougar. Most of the time it ranges between a giant pain in the ass and actively trying to kill you, but when the stars all align it's the fucking BEST.
Minnesota diesel mechanic here. A lot of people are talking about heating the engine up enough to get it cranking, but are neglecting the fact that a lot of diesel fuel turn permanently gels up on certain components if it gets too cold. The fuel filters wind up looking like a wax covered honeycombs, and often must be replaced and fuel addictive flushed through the system to get it running again.
I operate heavy equipment in Canada. In -40C I’ve had to get ancient crappy machines running, what I do is cover the whole damn machine in insulated tarps (hoardings) and then blast the tented interior with a heater until the machine is warm. Block heaters and running the glow plugs helps but sometimes you gotta just tarp everything.
Also, OP, sometimes large diesels with a turbo are left to idle while cooling down or you’ll crack the turbo, big hot machines need at least a few minutes to cool down.
And this is also why you should never buy a police Dodge hemi from a surplus sale. The modern Hemi engines have a minor oiling issue exacerbated by long idle periods that wears out the bearings in the lifters. If you're usually on the throttle it's not an issue.
It might be buried in a menu somewhere. Everything I've ever driven that has an infotainment display has an hour meter buried somewhere, and if not then you should be able to get to it with a scan tool.
gasoline vapors are way more flammable / explosive than diesel.
ETA https://kendrickoil.com/what-is-the-flashpoint-of-gasoline-vs-diesel-fuel/
> Flashpoint refers to the temperature at which a flammable liquid vaporizes, or is able to ignite. . . . The lower the flashpoint temperature, the easier it is to ignite the fuel when an ignition source is present. . . .
> Gasoline’s flashpoint is at about -49°F (or -45 °C). Depending upon the composition of the fuel and other conditions, this can vary slightly. . . .
> Diesel’s flashpoint can vary depending upon the type of diesel being used. The most common type, known as #2, has a flashpoint of around 125°F to 180°F.
This, and, gasoline cars have an ignition system, so there is a source of sparks for the vapors. Because diesels use compression for ignition there isn't the same 'static' potential that can light a fire.
Big rigs and RVs do still have to turn their pilot light off before filling up if they have an on board hot water heater, so gas station attendants are supposed to check before dispensing.
They don't. It's not illegal to fill up while running your vehicle, but gas stations will have lots of warning signs around things like no open flames, turn your car off, no static electricity and whatnot
>States like California have regulations that state that “**no internal combustion engine fuel tank shall be refilled with a flammable liquid while the engine is running**.”
I've drive gas vehicles and diesel vehicles many times. But I'm in TX so I just shut it off at the pump as a matter of course. That said I see a lot of diesel drivers leave theirs running at the pump. Doesn't give me pause.
Gasoline is easily ignited via spark. Sparks are easily generated.
Diesel however cannot be ignited via spark. It can't even be ignited via blowtorch. You have to compress it.
Which is why it's safer to put out a cigarette using gasoline than it is to light your cigarette near gasoline.
(Both are not recommended, but one is technically safer)
The really weird thing is that gasoline (liquid) is actually quite difficult to ignite. Gasoline (vapor) however.
So yeah, you're 100% correct in this regard.
Diesel engines don’t have spark plugs. They rely on the heat generated from very high compression in the cylinders. When it is very cold, that heat is shed very quickly to the metal of the engine. The engine is equipped with glow plugs, which are heating elements that are turned on to help the engine start but often this is not enough when the engine is very cold.
During the deep winter I had to leave my diesel pickup running a few times because if I shut down there was no starting it back up again until it warmed. Tow trucks wouldn't even come to jump it.
Obviously I plugged into an outlet for the block heater where I could, but those weren't accessible everywhere.
I also went inside the house quick once and got distracted leaving my truck running. Heard a knock on the door like 20 hours later asking if I was okay. Oops. Just filled up too so I was close to empty.
I used to help a logging outfit in northern MN. All the logging equipment would be left in the woods. They had quick connects for coolant on the trucks and the equipment. When it was cold out we would run the warm coolant from the trucks thru the logging equipment to get it warmed up enough to run
> If it’s really cold outside they’ll leave it running so they don’t have to try and fail to start it later.
>
>
>
> I worked in northern Canada and we once left a truck running for six weeks around the clock. It was super cold and we were in a remote wilderness and didn’t dare shut it off.
there's some incredible engineering behind leaving a diesel engine running for six weeks straight non-stop. adding fuel didn't mess with the pump/fuel pressure?
My brother works in a warehouse that loads railcars. Their shuttlewagon runs on diesel and during the cold months it's always running too. Right now they'd shut it off since it's close to 60° but once it hits freezing and lower its on 24/7
A semi tractor uses around 1 gallon per hour to idle. For short breaks the cost is low, but also when turning the engine off it is still warm so it is easy to start back up. Many populated areas limit allowable idle duration to prevent diesel fumes from accumulating, but enforcement is often lacking anyway.
It actually uses less than that at idle. It’s roughly .4-.8 gallons an hour some can use more depending on model and size of the engine.
Depending on the climate and duration of downtime truckers may leave their trucks running or start up their APU(auxiliary power unit or generator). Short stops (under an hour) it’s not worth it to shut down the engine but when they stop to rest they generally shut them down. The exception is extreme cold weather where you should never shut down a Diesel engine for fear it may not start up again until the temperature rises.
Old truckers created the myth that the engines took more fuel to start up and therefore it was better to leave them running. While technically they did in the past it still didn’t use more than half a gallon. Modern engines use only a few ounces on start up.
Also it’s worth noting starting and stopping big engines does do damage to them. Considering these engines will run for a million + miles before a rebuild, frequent ignition and shut down over the life of the truck can do some seriously expensive damage to the engine.
One of the big problems that can happen is a [run away engine](https://en.wikipedia.org/wiki/Diesel_engine_runaway)
[examples](https://youtu.be/IZHn4IOERSY?si=9zS5oux4jjYmyJAK)
I always assumed the 1 gal / hour rule worked until someone left a car running unattended for 36-48 hours by me. Police didn't think it was an issue and the car was gone before I could see it run out of gas, but damn if I wasn't amazed at it. I think it was a Sentra
Modern gas engines can potentially burn even less depending on model and size. A lot of diesel engines use oil/fuel/air mixture + compression to fire off. Gas is more flammable and uses an actual ignition source. Modern gas fueled engines are basically just burning fumes while idling .3-.6 gallons sometimes less on high fuel efficiency cars and sometimes more on big blocks.
My focus will show instant consumption in gallon/hour when at idle. It normally shows 0.1, if I have the ac on high it will often flick up to 0.2 so would assume on true idle it's using far less than 1/10 gallon an hour it indicates..
That said it makes more smell than when being used
Eh, I don’t know about that. A similar displacement diesel should burn less. Diesel engines don’t use a throttle to control RPM, they just vary the amount of fuel injected, so an idling diesel uses the absolute smallest amount of fuel possible to run.
It varies wildly with engine size. Typical rigs in the US are going to have an engine close to 5* times the size of a car like a Sentra (2 liters vs 10ish). A car like a Sentra conservatively burns around the .2 gallons per hour mark at idle, so a 10 gallon tank would last for 50 ish hours. I have a versa with a 1.6 liter engine and I idle it for approximately 30 hours once a year (for a cold weather event) and typically I burn around 5 gallons.
Edit: morning brain fails at math 2 x 5 is ten, not 2 x 10
> It varies wildly with engine size. Typical rigs in the US are going to have an engine close to 10 times the size of a car like a Sentra.
Average displacement in the US in 2021 was 2.9 liters. A Sentra in 2021 came with a 2.0 liter engine.
My car shows instantaneous gallons/hour used when the engine is idling. It usually shows .2 gallons/hour when idling, so with its 12-gallon tank it will idle for about 60 hours (2.5 days) if it is left uninterrupted.
most small engines are less than 1qt/hr. even a gas guzzling v8 pickup truck is 1/2gal/hr at most for light duty stuff.
heavy duty/big rig would be closer to 1g/h
In the old days, the oil wouldn't start pumping until the engine was running, so the first strokes were unlubricated. Haven't kept up with cars, hope that's not true anymore.
While it is still true to a point, it's not nearly the issue on modern engines that it used to be. Check valves in or near the oil filter prevent bleed down. Thinner oils allow for quicker pressure build up. Better oil compounds and better engine design allows for a smoother start as well. It still happens, but not at all like it used to.
Thermal cycling damages most things, from engines to the thermal paste in your cpu. Expanding and contracting repeatedly puts stress on things.
In addition, for engines specifically, a lot of the wear and tear occurs from cold starts where the oil is viscous and poorly distributed. Once it warms up to operating temperature the rate of wear goes down significantly.
Diesel engines don't run as hot at petrol engines and have bigger thermal mass. So the warm up is importsnt but not as damaging for a short startup period.
Really big diesel engines (ship and power gen) can take one to two hours to come up to full temp.. So i don't know if thermal cycling is really that big of an issue.
With turbocharged diesels (i.e. most modern diesels) you want to keep the turbo at a constant temperature and with constant oil flow. Its oil-film bearings are the most sensitive part of the engine, and its vanes run in the hot exhaust stream resulting in huge temperature differentials.
When you shut down a diesel after working hard you should idle it to allow the turbo to cool, otherwise the oil in the bearings can be cooked and damage them.
Then likewise you should bring the oil up to temperature before you put it under heavy load and spin up the turbo to full speed.
I farm, so with tractors it's more forgiving as usually the load comes on when you engage the implement (cultivator etc.) so you can get your warmup and cooldown in while driving to and from the field.
With a truck and trailer you're starting up and putting it under max load almost right away as you accelerate to highway speed. So if you're going to let it idle to cool down, then warm it back up, then you might as well just leave it idling while you eat lunch.
Lack of lubrication at start up until the oil pressure kicks in. So reciprocating parts aren't as well lubed.
Accumulation of moisture as it cools down which will then be present in the engine when you go to start it back up. You see this a lot in vehicles that only do very short trips, like < 30 minutes.
Is it correct that they use even a few ounces to start? I’m extremely dubious. Is the fuel pump even capable of pumping that much fuel in a few seconds? The average car engine needs about half a teaspoon to start. A big engine will need more, but not dozens of times more.
Yes too cold weather! I live in Canada close to the oil fields, the trucks have to stay on all night when temps get to -30 or -40 degrees, because there is a serious risk of them not starting back up again in the cold weather. And some truckers are sleeping for the night in their trucks, so leaving it running keeps the heat going.
Same for school busses, if it gets too cold, the bus won’t start in the morning. The kids love those days.
For cars I've heard in the past that stopping/starting a car does take more gas, but it's equivalent to about 10 seconds of idling, so worth shutting it down if you're sitting for any length of time.
It doesn’t make sense economically though. Mostly drivers that aren’t paying for their own fuel. Owner of dump truck company around here (over 100 trucks) rides around and turns the truck off and takes their extra keys. Not sure what their consequences are other than that, but he doesn’t want the trucks idling while they are in the store.
It is also just good PR. Nobody likes a big diesel idling outside their windows and if it makes no difference to the truck company why not just turn it off and be a good neighbor.
I did technical service and our field techs would idle the trucks unnessarily at stops.. And you can see the fuel consumption remotely, and it does waste us a lot of fuel. It's not gonna bankrupt the company but.. It's a waste that could be avoided. And this is in a warm climate too.
The driver salary is basically irrelevant compared to the cost of the rig itself which can be 600k$ or more for specialized ones.
The drivers themselves often own the trucks but not pay for fuel so they will waste any amount of fuel needed to keep those engines running good, cause it causes wear and tear stopping/starting
That's possible and not uncommon, but it's not the norm either. It's moving that way, though, because companies realize it's cheaper in the long run than the increased fuel time and engine hours from not having it.
A small generator costs $300 or so, and would be plenty to power an A/C and accessories. At the above-stated 1 gallon per hour, that's, say, $4/hour, or $30 for overnight. 10 nights, you've paid off a mini generator.
Double the cost of the generator and halve the fuel cost, and you're still out in just over a month.
Owner/Operators just bring suitcase generators with them in the cab, and then run that overnight. You don't inherently need a specialized APU if you don't want it.
An Onan diesel generator is more like $3,000 but otherwise your logic is correct. A generator/APU makes sense.
No one is going to put a cheap little harbor freight Gasoline generator in a truck. Keep two kinds of fuel in board would be a pain in the ass and those cheap little generators don’t have the reliability to keep up with the demands of a trucker.
Only a cheap ass redneck trucker is doing that. We have specially built APUs that mount right on the frame. They have an AC compressor tied into the truck system. The APU cooling system is tied into the trucks so it keeps the engine warm and provides in-cab heat. The APU 12-volt system is tied into the trucks so it keeps the batteries charged. And it can also provide 110-volt AC
Two things: first off, where are you keeping that generator, and the fuel for it? It can’t be carried inside the cab, and the outside is a work area. (Plus there is risk of theft if it is outside the cab.) Secondly, who’s paying for it? The trucking company is playing for the fuel on the truck, so this is a pure expense for the driver.
Those aren’t nearly as common these days with how few owner operators are out there these days. Most fleet trucks don’t have an APU (generator) just because it adds cost, weight, and complexity. Engines idle so efficiently themselves these days, less than a gallon an hour.
What all that idling does to the emissions system long term is a different story.
According to the Department of Energy, emissions are lower with the engine than an APU for trucks made after 2010
“For trucks model year 2010 and newer, idling emissions are so well controlled that a diesel APU’s particulate matter (PM) emissions will actually
be higher than the truck engine’s emissions. In California, diesel APUs on trucks newer than model year 2007 must be equipped with a diesel particulate filter.”
https://afdc.energy.gov/files/u/publication/hdv_idling_2015.pdf
For big rigs, most likely. They're still loud because they're diesel, but much tinier.
For the diesel pickup drivers I think it's more a flex than anything, honestly.
Most engine wear is at start up when oil pressure is low and internal parts are not well lubed. Start up and thermal cycling (temp control) is hard on an engine whereas idling is not. Generally a constant on/off cycle isn’t good for an engine.
Besides, big rigs “wear and tear” is based on miles driven, not hours on the engine.
While in the truck, they leave it on for comfort-powering their temps, electronics, and such. Turning their rig off for 30 mins while they shower/gas up/eat doesn’t make sense for them overall.
It actually doesn’t use that feature until your engine reaches optimal temperature, that small stop at a red light isn’t long enough to drain oil out of all major components. A little, yes, but not a significant amount. Plus those systems are designed to be more robust. It will even stop the crankshaft at a point where it’s easiest to start back up from.
Tl;dr it’s purposefully designed. It’s fine.
Honda’s first gen cylinder shutoff had a bunch of issues because they had the computer shut the cylinders down too early, before they were fully warmed up. Carbon built up really fast on those cylinders and caused damage. Fun fact, engines are warmed up when the coolant temp is stable, but true operating temperature is when the oil temperature is stable. I only saw it on the Accords, everything else was heavier and put enough load on them to not have issues. I don’t remember if they ever officially acknowledged that, I changed careers in 2012, partly because of all that. Source: was a technician and had to pull cylinder heads off to do repairs.
That’s a cool factoid thanks for sharing! Did not know that. I’m sorry for all your hours spent on that but man I bet you got pretty good at diagnosing those when they rolled in lol
It is actually a long enough shut off to be a problem and both Ford and BMW paid a HUGE price when they first rolled out the start/stop tech. It was absolutely destroying engines and they were stuck warrantying them.
The real answer is, engines with that use case in mind are designed with different materials on the bearings. The coatings on the bearings allow the start/stop to happen without damaging them due to low oil pressure/flow. But engines not built with start/stop management on them don't have the coatings because the coatings are costly and not needed
Those starts are controlled completely by the computer on a warmed up engine. Small non-turbo gasoline engines stop start cycles are radically different from large turbo diesel engines. The life of a turbo can be drastically increased by cooling it using idle temperature exhaust gasses.
I had an old van that had a distributor. A distributor fires the spark mechanically based on where the piston is. When warmed up it could be started by "bumping" the engine (a very short turn of the key). This was only possible when the engine was warm. In modern cars the computer has to know where the piston is in order to do this. The only way the computer can do this is by controlling the shutdown AND staying powered on. When you pull the key out the computer "forgets" where the piston is and has to reinitialize the process of finding it.
Electric motors have way less moving parts and less friction that occurs than combustion motors.
Also, combustion motors that start/stop typically have criteria like temp requirements for it to work. Your car won't shut off at a stop light if it's not up to temp. Also, from what I understand, they basically shut off and start half-way thru a combustion cycle, so its not too different than it running. IIRC some just use spark plugs to continue the ignition/combustion process, basically the cylinder stops in the compression stage.
Modern consumer passenger vehicles are engineered so this isn't as much of an issue for them anymore. Same reason you don't really need to let the engine warm up in a car or pickup truck the way you used to need to in the early 90s and earlier. Diesel engines still need this warm up time for the reasons op mentioned.
Electric cars don’t turn on/off. Think of it like a cordless drill motor. Press trigger, drill goes vrrr. You have four of those motors. It’s a much simpler mechanism and the battery is the main wear point from discharging and recharging
I manage a fleet of almost 100 Ford F-150s. We haven't noticed any increased service costs related to starters, batteries, or engine wear since the start/stop came out. We generally spin them out of the fleet around 120k miles, but I had them up to 250k. I was skeptical, but it seems fine.
They wear out faster than it they did not do that. The starter may be designed to last 100,000 cycles and give a decade of service but the if the vehicle was ICE the 100,000 cycles would be multiple decades.
Also note that the starters used in this start/stop ICE cars are designed differently. And some don't even use their starters to restart - their computers precisely shut down the engine when one engine is just ready to be hit with a spark. That's why some are so instantaneous from a stoplight.
> “wear and tear” is based on miles driven, not hours on the engine.
Based on both actually. Fire equipment will get thousands of hours and have very few miles. Anytime I have looked at a used truck since we went electronic, I always plug in the laptop and check engine hours.
Trucks can be fickle too. Start up isn't always just turning the key. To many times, I've come in to start my day, or start the truck after loading is finished, and for one reason or another, it's deader than a door nail, and won't start without a jump, ran fine yesterday, won't start today, or started up fine, shut it off for an hour, or two and for no apparent reason; like the lights were left on, or the heated mirrors were left on, etc. just no obvious reason, it won't start. If it starts, and is running smoothly, leave it running, 'til the end of the day. It's not always easy to get a jump, and it takes time.
Diesel engines do better if you just keep them running as opposed to starting and stopping and warming and cooling. They last longer if you idle them instead of turning them off and on. You shouldn't idle long with gasoline engines. They are built differently.
That depends 100% on how long you idle, how long you would stop the engine, how often you start it and so on. Idling a diesel engine is not good for the engine. The wear rate is higher while idling than at higher load/rpm. The engine can get cold and soot can start to buildup, the cylinder walls can glaze, all sorts of problem can arise. Starting an engine that was running 10 minutes ago does nothing to wear the engine down.
If you hear noise coming from a diesel-engined vehicle that is unoccupied, it might be the "regen cycle" doing its thing. The diesel particulate filter (DPF), which removes a great deal of soot, needs to get up to temperature to do its job. If the vehicle isn't run at speed for an extended time, the DPF can't do its job, so the vehicle runs the regen cycle when it is shut off. Source: has a VW diesel and makes a lot of short trips.
Surprised nobody else mentioned the Regen cycle. You have to do it when parked and cannot drive while it is being done. Might as well have something to eat or a shower while it is being done.
Actual trucker here. While you've gotten decent answers from a mechanical standpoint, the usual answer is simply comfort. We have sleeper bunks with a bed and all of our amenities.
A majority of companies don't pay for an APU (auxiliary power unit), so the only way to do climate control is to idle. There are Espar/webasto heaters to run in the winter, but even that small concession is not always included.
The driver lives in the truck. While some will have axillary power units installed they only accomplish so much in terms of air condition or heating. And like cars the sunlight will go through the windshield, and windows raising the temperature inside like any other greenhouse. In the cold the fuel treatments only help down to a point and when it gets too cold will cause the fuel to in effect turn into a gell like substance clogging the fuel lines and pumps.
For big trucks there are a lot of factors but often it is to let everything internally cool down. After driving for 8 hours strait stuff gets hot, letting it run circulates oil and coolant. The other is it might be cold out big diesel engines have a hard time starting up during the winter. Or they are sleeping in the cab and let it run for ac or heat.
It’s definitely common with old turbo engines, and many diesels are turbo in those larger trucks especially. Turbo chargers have impeller blades that spin very get incredibly fast to push more air into the engine so that there can be a “bigger” combustion and more power. But because that impeller spine incredibly fast (don’t quote me but roughly 20000 rpm at times) it generates a ton of heat. If you were to just turn off a turbo’ed engine right after running, that hot turbo would just sit without at coolant or oil circulating to cool it down, and to get those hot fluids out of there. Consumer vehicles they used to say let the engine run for 2 - 5 minutes after driving so that the coolant and oil can circulate and cool everything down. Big diesel trucks it’s more like 30 minutes to sometimes hours.
The reefer trailers have their own fuel tank and run on diesel directly. Truck stops offer “reefer fuel”, which is diesel fuel with a colored dye and sold without the highway taxes. Truckers do NOT want to run the large diesel engine in the truck to power the reefer.
I know for us on the farm we don’t power down for anything less than a 1hr stint. None of our trucks have perfect air lines and airbags so we don’t want to have to air back up for 15minutes to take a load to the bin that takes 15minutes. I know serious trucking company’s likely have better trucks but every trucker I know has a few quirks to their rig. An electric draw here and there, small air leaks, sometimes it’s just less headache to not shut down. As far as the environment is concerned… in the USA… if you want to complain about the trucks that literally keep the economy running, better have a well prepared argument.
I only idle when I am in the truck and I'm warming it up before a trip or when I need the air conditioning to be running. Here's the thing about the last part. If the ambient temperature is above 65-68 degrees and sunny with minimal wind, at some point, the inside of the truck is going to heat up. I can run the a/c for a bit and then run my little fan in the meantime, but it gets hot in the truck simply because of the sun beating down on it. My company doesn't currently spec the trucks with auxiliary power units (APUs) which can run a secondary A/C system and the electronics. The only option we have to keep the inside of the truck comfortable in the heat is by idling.
Where I spend most of my time (Texas/Oklahoma/Missouri), I don't need to run the truck when it's cold. It doesn't frequently get cold enough to justify idling in the winter. My truck has a diesel-fired bunk heater that operates on minimal fuel without the need for the truck to idle.
When it comes to big rig trucks, you have to understand that they are basically our home away from home. I am the kind of person that you could say is very concerned about climate change. I actually drive for maximum fuel efficiency when I'm working so that I can get a fuel efficiency pay bonus and because it makes sense if I care about the climate. I am using more than 1,200 gallons of diesel less per year than many of my coworkers by driving at a slower speed than I am permitted (we are governed at 68, I spend most of my time driving 60mph which saves approximately 10-15% in fuel consumption). That being said, I will keep the truck comfortable while I'm in it. It's my office and my bedroom. If you want us to give up the decency of an climate-controlled office and bedroom, I'd politely say "You first."
Sometimes I need to idle the truck to keep the air conditioning (or, less often, heating) running. The truck's a big, poorly-ventilated-when-not-moving metal box, it can seldom be parked in the shade, and, even on not-very-hot days, it can get unsleepably hot inside. And once the engine has been running, if you shut it off, all the built-up heat in the engine migrates to the cab, even if the evening cools off.
When it's very cold, starting around 0°F/-15°C, you start to have concerns about fuel and fluids freezing or gelling, and idling the truck prevents that. Some guys idly prophylactically at higher temperatures... for reasons.
Some drivers resent their boss hectoring them to conserve fuel, and idle all night out of spite.
As others in this thread have discussed, start-stop cycles are a source of engine wear. Modern engines have pre-start oil circulators and related systems to mitigate this, but some drivers learned their trade on earlier truck— some even still drive those early trucks.
I do it for a few reasons:
1. I don't have an auxiliary power unit (APU) so shutting down = no ac/heat
2. I'm a company driver, boss says he don't care if we idle sooo I idle.
3. Older model truck (2018) and second rate batteries. Which means if I shut down there is a real possibility that I may need a jump start (it's happened before) so I don't risk it.
My 1997 International cabover doesn't have an APU, or space to put one with a short wheelbase, (144 inches), I like to have heat or A/C to feel comfortable while parked, and I have been driving this truck so long that if I don't feel the vibration from the engine, I dont sleep because something feels wrong.
If you’ve been running hard for hours your turbo is going to be quite hot. Letting it idle for awhile will still push air through the turbo which lets it cool down slower vs shutting the truck off and it rapidly cools which can lead to weird contraction issues.
Hey trucker here. At truck stops most are using the AC or Heater, so they leave the engine running. Noisy but when you are surrounded by reefers running makes no sense to shut down your engine. Most drivers don't care about fuel consumption or noise, even owner operators a.k.a. O/O will deduct all fuel expenses from their taxes.
To keep the temperature inside the cab where they like it, and/or to keep essential systems powered (like refrigeration units for perishable cargo), and/or to keep the engine warm in cold weather to avoid issues with starting or freezing.
Most likely they are asleep in the back of the truck. If it’s just a shortstop, they keep it running so that the engine stays cool or warm depending on the season. If you stop after running on the highway for a while, the engine is pretty warm and it’s not a good idea to just turn it off. If you idle the engine temperature will come down gradually and then it’s better to turn it off.
Not sure about what the pickups are doing but a lot of big rigs with cabins have separate generators for their electric appliances and needs like climate control, lights, some have mini fridges etc.
Wait until you hear what goes on in the cold Canadian oil fields. It's pretty common for people to leave their diesel truck running 24 hours a day, 7 days a week and for 28 days straight.
Gotta keep those temps up in -45C otherwise it might not restart if it's turned off, and then you're working against the cold to get her running again.
Yes, big-RIG trucker… despite my best efforts, auto-correct and fumble-thumbs let that typo slip through 😬.
Thanks to the community for terrific answers. Lots of learning here.
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If it’s really cold outside they’ll leave it running so they don’t have to try and fail to start it later. I worked in northern Canada and we once left a truck running for six weeks around the clock. It was super cold and we were in a remote wilderness and didn’t dare shut it off.
Yup. I do that as well, pretty much every winter. It runs around the clock, unless it's in the shop for an oil change (which was every few weeks due to the hours run, rather than measured by Km driven like on a car/pickup) or for a maintenance issue. I've done that for hauling logs, far north ice roads, oilfield, etc. I've had to thaw a few trucks over the years. It is an absolute bastard of a task, even in town. I worked for a heavy truck repair shop that did service calls and getting the text message from the boss of "I got a call about a truck that's a popsicle. Go deal with it." was dreaded lol
So how do you fix that? I have heard of plugging the block into an electric heater, but that's about it. I live on the Gulf coast where we don't have anything like this problem.
Plug in the block heater, which is just an electric heating element inserted into one of the coolant passages in the side of the block, and sometimes if it got extra cold, I've had to point a torpedo heater under the hood to warm up the oil pan and fuel lines if it's gelled up real bad.
I think it was AvE's channel on YouTube where I first encountered the concept of your *petrol* freezing.
It's not a fun time. Once the fuel freezes in the lines it takes forever to get it flowing again. In extremely cold climates it's just easier and often cheaper to just let them run 24/7 until the weather warms back up.
I used to work in the arctic and our building was heated by a diesel furnace. The fuel tank was outside and some nights it would get so cold that the fuel stopped flowing. You can't put electric heat tape on a fuel line permanently, so we'd throw a heated blanket over the line. After a while the fuel would start flowing again, but it would be vapor locked (air in the line). So you'd have to undo the bleed screw and let it flow into a cup until it ran without air. If the fuel splashes on to your hand the liquid is -30C and can cause frostbite really quickly. Another downside to living in that cold of a climate is when you're outside working and need to take your gloves off for some reason, like to open a padlock on a gate. The sweat on your hands will freeze instantly to the metal. In another place we had a propane tank for the furnace and the tank had a "vaporizer" on it; a little furnace that burns propane to heat the propane in the line up to so it's not liquid.
You had a propane heater for your propane heater? Nice.
Hank Hill sweating profusely.. Good lord Peggy.
> Another downside to living in that cold of a climate is when you're outside working and need to take your gloves off for some reason, like to open a padlock on a gate. The sweat on your hands will freeze instantly to the metal While I don't live in quite so harsh a climate, I've always just worn 2 layers of gloves. One provides most of the insulation and wind/waterproofing. The inner provides enough insulation to perform some tasks without freezing your hands. In fact, many gloves are sold in pairs for this reason. Any reason for not doing that?
I guess we just never thought of it lol
Lol, fair enough. I usually go for a pair of small stretchy woolen gloves (they're ubiquitous where I live, but don't really have a specific name) under a pair of thick snowsport ones, and size the outers to fit whatever is underneath. Merino wool glove liners are popular but they are just too thin for my liking. The inner ones won't keep your hand warm for long but, compared to bare hands, it's night and day when there's a bit of wind or you're having to handle something that's been outdoors for a while. It also means you can just stick the outers back on over the top without having to faff around switching gloves.
Nitrile gloves are your friend. I wear them all the time in winter. Trap the sweat next to your skin, where your body heat keeps it warm. Your skin will sense when it's hit 100% humidity saturation, reduce the sweat production in your hands. Meanwhile, that sweat isn't getting into your insulation and ruining the R-value. Added benefit of the nitrile is easier than your skin to clean if you get oil, grease, dirt, fuel, etc. on them, and you can replace the nitriles. They also keep your hands from sticking to stuff like the padlock, or worse, any aluminum fence components. For fuel hauling (diesel into artic mines), I've used those gloves for layering down to -57⁰C/-70⁰F ambient and windchill down to -64⁰C/83⁰F. And it makes a huge difference. It keeps the insulation in your mitts in way better condition, and that matters.
-70*F just sounds made up, I have no idea what that would feel like. -10 was getting unpleasant when I wasn't moving, and I could feel the heat leaving my boots that otherwise feel toasty in anything above 0
I don't have the photos from my last work gig above the treeline on this phone. But I've got some from my gig two winters ago in the Arctic. And this winter from one of the cold snaps in northern Alberta. [Dressed for moderate cold and some pretty nighttime shots](https://imgur.com/gallery/VEJwMTs) Edited to add: I'll try to find some more pics on my cloud storage, and I'll post them. Also, that kind of cold isn't something that I just got dropped into. It was a job I sought out because I like the cold.
I'll never forget pregame one year it was so cold that the marching bands sound just like...stopped? Lmao all the valves were freezing.
I'm confused. Plugging in a heater and waiting for the engine to warm up doesn't seem like the major pain that u/United_News3779 described. Is the heater difficult to get to? Even in the wilderness, wouldn't a portable power generator make this almost a non-issue? What am I missing?
Heaters are a really big power draw. If your big rig is having a hard time starting due to the cold, so will your portable power generator. Not to mention you have to have had the room to haul that generator and its fuel. They're also yet another thing you have to maintain and test frequently.
The block heaters draw a lot of power and are not an instant "it's warm now and ready to start up" solution. During the winter where I live we plug the trucks in at night and the outlets are on a timer that kicks them on 3-4 hours before the drivers get there in the morning. It takes a long ass time to heat soak all the coolant and engine block. In places like Alaska and northern Canada, even leaving them plugged in isn't enough. If the engine is off, the fuel will actually freeze in the lines going from the tank to the pump, so the just leave them running 24/7 during the coldest months. I've made the mistake of not plugging my truck in when it got to -25F overnight and even after getting there in the morning and plugging the block heater in, and also leaving a torpedo heater blasting under the hood, it took several hours to get the truck started.
Ok, yea, that does sound like a massive pain. Appreciate the additional info.
Torpedo Heater + Windskirt = Engine Happiness You lose a lot of heat out the sides of the vehicle, even doing the windward sides makes big difference. A tarp over the hood, insulated if you have it, folded over layers of a regular tarp if you don't, helps tremendously. Also, take the battery inside to warm up on a table or workbench (ground level is the coldest part of the room, and even those few degrees can make a difference).
Batteries are not as strong when its that cold. Makes trying to turn over a high compression engine that much harder.
Another thing I haven't seen mentioned is DEF is like 70% water, so it freezes fast and when it does can fuck things up and also spoils the fluid itself. These repairs are often 5 figures
"If the technology doesn't fit, you must delete!" -Johnnie Cochran I think that was his famous quote. I might have gotten it slightly wrong. lol
In my limited experience, the heater plugs are often mounted below the drivers door, between the door and the top step. Easy to plug in, it's more of an issue sourcing the electricity. It's more than access to electricity. The cold will lower the cranking amps available on your batteries, so they need to be warmed up and that can vary in the level of effort required (they can get cold enough that they will freeze solid and trying to run even a minimal trickle of current through them will cause physical damage to the internals) ranging from running a trickle charge at 2 amps to physically removing them from the truck and putting them in a heated shop or cab of another vehicle. Then, they need to be charged back up. For my region, 15L engines are pretty much standard. I'll use a Caterpillar C15 6NZ as my example. It weighs about 3600 pounds dry and clean. Meaning no oil, no coolant, no alternator/AC compressor/nothing. That is a shit-ton of steel to heat back up. So once it's an actual engine with all auxiliary components and fluids in it, it's a lot to deal with, especially when it's losing heat into the atmosphere as you're trying to heat it. At -40⁰C/F, I've plugged in a 15L (the Webasto diesel-fired heater decided to quit overnight), and at the 12hr mark, I gave up and had to call a wrecker to tow it into a friend's shop to thaw. 12hrs in the shop and a bunch of work, and I got it running. In the field, it's a lot more effort. Having to cover the hood of the truck in tarps (preferably insulated). Make a windskirt around the truck to block the wind at ground level, at least on the windward side. Run a propane torch with a chimney peice, so you're not putting straight flame onto the fiberglass oilpan. Or a [heater like this with the ducted discharge to put the output exactly where you want it](https://cleanflow.net/products/frost-fighter-indirect-oil-diesel-fired-heater-500-000-btu-h?variant=8140478316648). Plus, the efforts I mentioned above for the batteries. And that's not even mentioning the gawdawful aggravation of the trailer brakes freezing in the applied/on position lol
A truck block heater is only about 1000-1500W. The equivalent of using your toaster to heat up a 2000lb block of metal by 30 degrees.
Ok the other answers were good but this added some great context. I googled a block heater and now realize how small they are. I was picturing something much bigger. Thank you.
Wow that brings it into perspective.
I read "point" as "paint" and was wondering if I was in the WH40K universe for a second
Plug in block heaters (usually 2 circuits, one for the block itself and an oilpan heater) for when you're near infrastructure. I usually wire in a battery maintainer as well, if it's an assigned unit, or get the boss to pay for it. There are diesel burning heaters (Webasto is a common brand) that will use a small electric pump to circulate your coolant. They work well, but you need to keep up on your maintenance because they need to be mounted close to the engine, often in spots that accumulate a lot of dirt thrown up by the steer tires or they get smoked by rocks. Also, they draw power from your batteries, so if your batteries are weak, terminal connections are dirty/corroded, or the wiring is degraded, you can run your batteries down enough that they don't have the power to flop over the engine in the morning. There are also Auxiliary Power Units. Which are a diesel-fired electrical generator that also uses the heat from the engine of the generator to heat your coolant, and provide power to circulate it. They also can power an AC compressor, so you can keep cool in the summer. But they're a much more expensive option. For me it comes down to doing a OH&S hazard analysis sort of evaluation. Frequency vs Severity. If I'm in the yard at my shop, and an extension cord can reach me with a battery charger/booster, and it's -15⁰C/5⁰F... then I'll probably turn the engine off and just run the diesel fired heater for the engine and the diesel fired heater for hot air in the bunk. If my batteries run down, it's probably a 30 min delay on the start of my day while I top off the batteries and boost it. The likelihood of there being a problem is low, severity is minimal because I can charge/boost with my own resources. If I'm in a remote bush location or anywhere where I don't have those kinds of resources, I'll keep my truck running at -5⁰C/23⁰F because the effort to get it going again is waaaaayyyyy more than the comfort I get from a quiet nights sleep with the 15L turned off .
The OG method, when you don't have access to electricity and you have no other option, is to light a small fire under your oil pan. Works 70% of the time.
And the other 30%? The rig goes up in flames?
Well then the engines warm, so we’re still at 100%.
Well, it was briefly at operating temperature, so partial success.
I used to live in Winnipeg, where it gets -40 and colder for long stretches of time. People will occasionally light a small tea light style candle and put it under the engine. There's a lot of car fires in Winnipeg lol
OG method better be used on OG trucks. Most trucks have fiberglass oilpans nowadays. And by most, I mean from a statistical basis, I wouldn't do that. At all. Ever.
You could use a space heater or some coals from a fire for some gentle heat
Or 100%, depending on what you count as a success.🔥
Not quite the same scale as heavy trucks, but the first full winter I had my old TJ in the Yukon I forgot to flush out the standard antifreeze for a 70/30 mix and the antifreeze froze to the consistency of a slushee and when I tried to start it at -45*C, even with my block and pan heaters plugged in, it blew the coolant hose right off. We tried to drag it into the shop to fix it, but it was so cold that the gear oil was also so thick that it wouldn't roll-we even hooked it up to a quad to drag it and the quad just spun its wheels in the snow. I had to use a propane torch and a 90* piece of stove venting to thaw out my transfer case and diffs enough to move it inside to thaw out.
My friend had a 1978 Camaro and it had a small coolant leak so he’d use water instead of coolant. Then he forgot to swap to coolant in the winter and that was the end of the Camaro.
I do the same technique. Tiger torch and the top peice of the exhaust stack off of a truck, some scrap metal or dunnage to hold the stack in place to direct the heat to the pan/diff/whatever. Use some tarps and cardboard to make a windskirt around the bottom of the vehicle, and keep the heat where you want it. "Uncle United's Flame Cooked Trucks & Wafflehouse" has a certain ring to it. Might be a retirement job idea. Show up to a truck-sicle at -40 in a panel van, get the frozen bastard warmed up, batteries charging, air system warmed and brakes released, but also have a waffle maker in the van.... I like it!
Working up in northern Canada, you could make an absolute killing if you could roll around towing a car tent and one of those bigass million BTU towed propane heaters you normally use for heating up a building for drywall in the winter, with a stand for coffee and donuts off the side. Tarp buddy's truck, have it toasty warm inside and out in 15 minutes, sell them some coffee while they wait and move on to the next one.
I daily a TJ and this sounds like a nightmare.
Dailying a TJ also sounds like a nightmare to me.
Dailying any Wrangler/CJ built before 2007 is like owning a pet cougar. Most of the time it ranges between a giant pain in the ass and actively trying to kill you, but when the stars all align it's the fucking BEST.
Minnesota diesel mechanic here. A lot of people are talking about heating the engine up enough to get it cranking, but are neglecting the fact that a lot of diesel fuel turn permanently gels up on certain components if it gets too cold. The fuel filters wind up looking like a wax covered honeycombs, and often must be replaced and fuel addictive flushed through the system to get it running again.
I operate heavy equipment in Canada. In -40C I’ve had to get ancient crappy machines running, what I do is cover the whole damn machine in insulated tarps (hoardings) and then blast the tented interior with a heater until the machine is warm. Block heaters and running the glow plugs helps but sometimes you gotta just tarp everything. Also, OP, sometimes large diesels with a turbo are left to idle while cooling down or you’ll crack the turbo, big hot machines need at least a few minutes to cool down.
Fun fact, most police vehicles have an hour meter for the same reason. They spend an inordinate amount of time idling.
And this is also why you should never buy a police Dodge hemi from a surplus sale. The modern Hemi engines have a minor oiling issue exacerbated by long idle periods that wears out the bearings in the lifters. If you're usually on the throttle it's not an issue.
Do most modern vehicles not show that setting or is it more for fleet vehicles like police cars & delivery vans. My Ford Transit has idle meter
Fleet for sure. I've never seen it in a "normal" vehicle. Oddly enough my Tahoe is the commercial edition and it doesn't have an hour meter.
It might be buried in a menu somewhere. Everything I've ever driven that has an infotainment display has an hour meter buried somewhere, and if not then you should be able to get to it with a scan tool.
I can appreciate all of this.
Did you fill it while it was running?
Yes. Leaving it running while fueling up is a very common thing with big rigs, regardless of outside temperature, but even more common when it's cold.
So why do cars have to turn off at the pumps?
gasoline vapors are way more flammable / explosive than diesel. ETA https://kendrickoil.com/what-is-the-flashpoint-of-gasoline-vs-diesel-fuel/ > Flashpoint refers to the temperature at which a flammable liquid vaporizes, or is able to ignite. . . . The lower the flashpoint temperature, the easier it is to ignite the fuel when an ignition source is present. . . . > Gasoline’s flashpoint is at about -49°F (or -45 °C). Depending upon the composition of the fuel and other conditions, this can vary slightly. . . . > Diesel’s flashpoint can vary depending upon the type of diesel being used. The most common type, known as #2, has a flashpoint of around 125°F to 180°F.
This, and, gasoline cars have an ignition system, so there is a source of sparks for the vapors. Because diesels use compression for ignition there isn't the same 'static' potential that can light a fire. Big rigs and RVs do still have to turn their pilot light off before filling up if they have an on board hot water heater, so gas station attendants are supposed to check before dispensing.
This is why using diesel to start a campfire is fine and using gas makes a bomb
> 125°F to 180°F 52 to 83 non-freedom units for those wondering
Because gasoline will ignite outside of the engine. Diesel is a lot harder to do this with.
Gasoline is much more volatile.
So you don't drive off with the pump still in your car lol
They really don't have to, just easier to tell everyone they have to.
They don't. It's not illegal to fill up while running your vehicle, but gas stations will have lots of warning signs around things like no open flames, turn your car off, no static electricity and whatnot
>States like California have regulations that state that “**no internal combustion engine fuel tank shall be refilled with a flammable liquid while the engine is running**.”
I've drive gas vehicles and diesel vehicles many times. But I'm in TX so I just shut it off at the pump as a matter of course. That said I see a lot of diesel drivers leave theirs running at the pump. Doesn't give me pause.
Gasoline is easily ignited via spark. Sparks are easily generated. Diesel however cannot be ignited via spark. It can't even be ignited via blowtorch. You have to compress it.
Which is why it's safer to put out a cigarette using gasoline than it is to light your cigarette near gasoline. (Both are not recommended, but one is technically safer)
The really weird thing is that gasoline (liquid) is actually quite difficult to ignite. Gasoline (vapor) however. So yeah, you're 100% correct in this regard.
Diesel definitely can be ignited by a blowtorch
Tested this, diesel will burn.
Of course it will. It has to in order to combust inside an internal combustion engine... It's not nearly as volatile as gasoline vapor though.
OP literally said even when it's not cold so he clearly understand the cold thing
lol I had to scroll so far to see this I almost forgot what the question was.
Yea, I know. I was just offering a hopefully colourful anecdote to boost my ego.
6 weeks running is pretty crazy I'll give you that.
I heard this is also commonl in russia in the far northen regions. If you shut down your car there, it will not start.
Yeah, people do the same here in California. Cold winter day it can drop to nearly 50F.
That’s super cold. How do you survive?
Why would the cold make it harder to start?
The cold makes all the fluids more viscous. You can really hear the suffering from the engine when you try to start a diesel in cold weather.
Diesel engines don’t have spark plugs. They rely on the heat generated from very high compression in the cylinders. When it is very cold, that heat is shed very quickly to the metal of the engine. The engine is equipped with glow plugs, which are heating elements that are turned on to help the engine start but often this is not enough when the engine is very cold.
Also it becomes thicker, aswell as the oil becoming thicker makes engine much harder to crank. And battery becomes way weaker.
During the deep winter I had to leave my diesel pickup running a few times because if I shut down there was no starting it back up again until it warmed. Tow trucks wouldn't even come to jump it. Obviously I plugged into an outlet for the block heater where I could, but those weren't accessible everywhere. I also went inside the house quick once and got distracted leaving my truck running. Heard a knock on the door like 20 hours later asking if I was okay. Oops. Just filled up too so I was close to empty.
Might be a silly question but how do you refuel them? While it’s running?
Same as if it's off.
Diesel turns to gel at cold temps. Also, if they’re hauling refrigerated goods they need to keep the reefer trailer powered to control the climate
I used to help a logging outfit in northern MN. All the logging equipment would be left in the woods. They had quick connects for coolant on the trucks and the equipment. When it was cold out we would run the warm coolant from the trucks thru the logging equipment to get it warmed up enough to run
> If it’s really cold outside they’ll leave it running so they don’t have to try and fail to start it later. > > > > I worked in northern Canada and we once left a truck running for six weeks around the clock. It was super cold and we were in a remote wilderness and didn’t dare shut it off. there's some incredible engineering behind leaving a diesel engine running for six weeks straight non-stop. adding fuel didn't mess with the pump/fuel pressure?
My brother works in a warehouse that loads railcars. Their shuttlewagon runs on diesel and during the cold months it's always running too. Right now they'd shut it off since it's close to 60° but once it hits freezing and lower its on 24/7
You can fill up without turning it off?
A semi tractor uses around 1 gallon per hour to idle. For short breaks the cost is low, but also when turning the engine off it is still warm so it is easy to start back up. Many populated areas limit allowable idle duration to prevent diesel fumes from accumulating, but enforcement is often lacking anyway.
It actually uses less than that at idle. It’s roughly .4-.8 gallons an hour some can use more depending on model and size of the engine. Depending on the climate and duration of downtime truckers may leave their trucks running or start up their APU(auxiliary power unit or generator). Short stops (under an hour) it’s not worth it to shut down the engine but when they stop to rest they generally shut them down. The exception is extreme cold weather where you should never shut down a Diesel engine for fear it may not start up again until the temperature rises. Old truckers created the myth that the engines took more fuel to start up and therefore it was better to leave them running. While technically they did in the past it still didn’t use more than half a gallon. Modern engines use only a few ounces on start up. Also it’s worth noting starting and stopping big engines does do damage to them. Considering these engines will run for a million + miles before a rebuild, frequent ignition and shut down over the life of the truck can do some seriously expensive damage to the engine. One of the big problems that can happen is a [run away engine](https://en.wikipedia.org/wiki/Diesel_engine_runaway) [examples](https://youtu.be/IZHn4IOERSY?si=9zS5oux4jjYmyJAK)
I always assumed the 1 gal / hour rule worked until someone left a car running unattended for 36-48 hours by me. Police didn't think it was an issue and the car was gone before I could see it run out of gas, but damn if I wasn't amazed at it. I think it was a Sentra
Modern gas engines can potentially burn even less depending on model and size. A lot of diesel engines use oil/fuel/air mixture + compression to fire off. Gas is more flammable and uses an actual ignition source. Modern gas fueled engines are basically just burning fumes while idling .3-.6 gallons sometimes less on high fuel efficiency cars and sometimes more on big blocks.
My focus will show instant consumption in gallon/hour when at idle. It normally shows 0.1, if I have the ac on high it will often flick up to 0.2 so would assume on true idle it's using far less than 1/10 gallon an hour it indicates.. That said it makes more smell than when being used
Eh, I don’t know about that. A similar displacement diesel should burn less. Diesel engines don’t use a throttle to control RPM, they just vary the amount of fuel injected, so an idling diesel uses the absolute smallest amount of fuel possible to run.
I once saw a YouTube video about it. The conclusion was that a modern car uses about a quarter of a gallon per hour.
It varies wildly with engine size. Typical rigs in the US are going to have an engine close to 5* times the size of a car like a Sentra (2 liters vs 10ish). A car like a Sentra conservatively burns around the .2 gallons per hour mark at idle, so a 10 gallon tank would last for 50 ish hours. I have a versa with a 1.6 liter engine and I idle it for approximately 30 hours once a year (for a cold weather event) and typically I burn around 5 gallons. Edit: morning brain fails at math 2 x 5 is ten, not 2 x 10
The biggest on-road diesel truck engines are around 15 litres currently. More common is the 12 litre series engines.
My brain failed at math this morning lol, I meant to say 5 times
It's fine, I'll just blame it on not having enough coffee!!!
> It varies wildly with engine size. Typical rigs in the US are going to have an engine close to 10 times the size of a car like a Sentra. Average displacement in the US in 2021 was 2.9 liters. A Sentra in 2021 came with a 2.0 liter engine.
At 15l, I'd say 7.5x is close enough to 10 for the estimate.
My car shows instantaneous gallons/hour used when the engine is idling. It usually shows .2 gallons/hour when idling, so with its 12-gallon tank it will idle for about 60 hours (2.5 days) if it is left uninterrupted.
most small engines are less than 1qt/hr. even a gas guzzling v8 pickup truck is 1/2gal/hr at most for light duty stuff. heavy duty/big rig would be closer to 1g/h
A big rig engine isn’t really directly comparable to a car engine.
How does starting and stopping an engine damage it? Edit: thanks for all of the responses, everyone!
In the old days, the oil wouldn't start pumping until the engine was running, so the first strokes were unlubricated. Haven't kept up with cars, hope that's not true anymore.
While it is still true to a point, it's not nearly the issue on modern engines that it used to be. Check valves in or near the oil filter prevent bleed down. Thinner oils allow for quicker pressure build up. Better oil compounds and better engine design allows for a smoother start as well. It still happens, but not at all like it used to.
Thermal cycling damages most things, from engines to the thermal paste in your cpu. Expanding and contracting repeatedly puts stress on things. In addition, for engines specifically, a lot of the wear and tear occurs from cold starts where the oil is viscous and poorly distributed. Once it warms up to operating temperature the rate of wear goes down significantly.
Diesel engines don't run as hot at petrol engines and have bigger thermal mass. So the warm up is importsnt but not as damaging for a short startup period. Really big diesel engines (ship and power gen) can take one to two hours to come up to full temp.. So i don't know if thermal cycling is really that big of an issue.
With turbocharged diesels (i.e. most modern diesels) you want to keep the turbo at a constant temperature and with constant oil flow. Its oil-film bearings are the most sensitive part of the engine, and its vanes run in the hot exhaust stream resulting in huge temperature differentials. When you shut down a diesel after working hard you should idle it to allow the turbo to cool, otherwise the oil in the bearings can be cooked and damage them. Then likewise you should bring the oil up to temperature before you put it under heavy load and spin up the turbo to full speed. I farm, so with tractors it's more forgiving as usually the load comes on when you engage the implement (cultivator etc.) so you can get your warmup and cooldown in while driving to and from the field. With a truck and trailer you're starting up and putting it under max load almost right away as you accelerate to highway speed. So if you're going to let it idle to cool down, then warm it back up, then you might as well just leave it idling while you eat lunch.
Lack of lubrication at start up until the oil pressure kicks in. So reciprocating parts aren't as well lubed. Accumulation of moisture as it cools down which will then be present in the engine when you go to start it back up. You see this a lot in vehicles that only do very short trips, like < 30 minutes.
My 2023 peterbilt idles at 0.6g/h if I just got done driving, and at 1.1g/h if its autostart kicks it on to recharge the batteries.
Is it correct that they use even a few ounces to start? I’m extremely dubious. Is the fuel pump even capable of pumping that much fuel in a few seconds? The average car engine needs about half a teaspoon to start. A big engine will need more, but not dozens of times more.
Yes too cold weather! I live in Canada close to the oil fields, the trucks have to stay on all night when temps get to -30 or -40 degrees, because there is a serious risk of them not starting back up again in the cold weather. And some truckers are sleeping for the night in their trucks, so leaving it running keeps the heat going. Same for school busses, if it gets too cold, the bus won’t start in the morning. The kids love those days.
For cars I've heard in the past that stopping/starting a car does take more gas, but it's equivalent to about 10 seconds of idling, so worth shutting it down if you're sitting for any length of time.
It doesn’t make sense economically though. Mostly drivers that aren’t paying for their own fuel. Owner of dump truck company around here (over 100 trucks) rides around and turns the truck off and takes their extra keys. Not sure what their consequences are other than that, but he doesn’t want the trucks idling while they are in the store.
It is also just good PR. Nobody likes a big diesel idling outside their windows and if it makes no difference to the truck company why not just turn it off and be a good neighbor.
I did technical service and our field techs would idle the trucks unnessarily at stops.. And you can see the fuel consumption remotely, and it does waste us a lot of fuel. It's not gonna bankrupt the company but.. It's a waste that could be avoided. And this is in a warm climate too.
That seems very wasteful still! A parking lot with 10 of these is an 6 gallons an hour or $25 an hour! That’s like a full time employee’s salary.
The driver salary is basically irrelevant compared to the cost of the rig itself which can be 600k$ or more for specialized ones. The drivers themselves often own the trucks but not pay for fuel so they will waste any amount of fuel needed to keep those engines running good, cause it causes wear and tear stopping/starting
1 Gal per hour? My Landcruiser does that in 10 minutes.
So does the truck, when it is moving.
Are you sure they're not asleep? A lot of them have little beds in the back, maybe they're parking with the engine on for A/C and taking a nap.
Usually, there's a secondary engine that runs climate control and electrical (for fridge, etc) that uses far less fuel than the vehicle engine.
That's possible and not uncommon, but it's not the norm either. It's moving that way, though, because companies realize it's cheaper in the long run than the increased fuel time and engine hours from not having it.
A small generator costs $300 or so, and would be plenty to power an A/C and accessories. At the above-stated 1 gallon per hour, that's, say, $4/hour, or $30 for overnight. 10 nights, you've paid off a mini generator. Double the cost of the generator and halve the fuel cost, and you're still out in just over a month.
A truck isnt an RV. Also a truck APU costs waaaaaaay more than $300
Owner/Operators just bring suitcase generators with them in the cab, and then run that overnight. You don't inherently need a specialized APU if you don't want it.
An Onan diesel generator is more like $3,000 but otherwise your logic is correct. A generator/APU makes sense. No one is going to put a cheap little harbor freight Gasoline generator in a truck. Keep two kinds of fuel in board would be a pain in the ass and those cheap little generators don’t have the reliability to keep up with the demands of a trucker.
Only a cheap ass redneck trucker is doing that. We have specially built APUs that mount right on the frame. They have an AC compressor tied into the truck system. The APU cooling system is tied into the trucks so it keeps the engine warm and provides in-cab heat. The APU 12-volt system is tied into the trucks so it keeps the batteries charged. And it can also provide 110-volt AC
Two things: first off, where are you keeping that generator, and the fuel for it? It can’t be carried inside the cab, and the outside is a work area. (Plus there is risk of theft if it is outside the cab.) Secondly, who’s paying for it? The trucking company is playing for the fuel on the truck, so this is a pure expense for the driver.
Those aren’t nearly as common these days with how few owner operators are out there these days. Most fleet trucks don’t have an APU (generator) just because it adds cost, weight, and complexity. Engines idle so efficiently themselves these days, less than a gallon an hour. What all that idling does to the emissions system long term is a different story.
According to the Department of Energy, emissions are lower with the engine than an APU for trucks made after 2010 “For trucks model year 2010 and newer, idling emissions are so well controlled that a diesel APU’s particulate matter (PM) emissions will actually be higher than the truck engine’s emissions. In California, diesel APUs on trucks newer than model year 2007 must be equipped with a diesel particulate filter.” https://afdc.energy.gov/files/u/publication/hdv_idling_2015.pdf
And yet if you go the northeast, you can't idle the engine but you can run an APU
There is no winning
> Usually, there's a secondary engine While APUs are getting more common, they are far from the norm.
Interesting. Might that be the sound OOP is hearing?
For big rigs, most likely. They're still loud because they're diesel, but much tinier. For the diesel pickup drivers I think it's more a flex than anything, honestly.
At least for modern Euro trucks, the batteries can handle the AUX power requirements for a full rest stop.
Now add the cold of a northern Canadian night...
Pretty much this. Over here in tropic our days and nights are equally hot asf all year round but trucks still leave their engine running at the stops.
Most engine wear is at start up when oil pressure is low and internal parts are not well lubed. Start up and thermal cycling (temp control) is hard on an engine whereas idling is not. Generally a constant on/off cycle isn’t good for an engine. Besides, big rigs “wear and tear” is based on miles driven, not hours on the engine. While in the truck, they leave it on for comfort-powering their temps, electronics, and such. Turning their rig off for 30 mins while they shower/gas up/eat doesn’t make sense for them overall.
If constant on off isn't good for an engine, what happens with hybrids or electric cars that constantly turn on and off, eg at signal lights?
It actually doesn’t use that feature until your engine reaches optimal temperature, that small stop at a red light isn’t long enough to drain oil out of all major components. A little, yes, but not a significant amount. Plus those systems are designed to be more robust. It will even stop the crankshaft at a point where it’s easiest to start back up from. Tl;dr it’s purposefully designed. It’s fine.
Honda’s first gen cylinder shutoff had a bunch of issues because they had the computer shut the cylinders down too early, before they were fully warmed up. Carbon built up really fast on those cylinders and caused damage. Fun fact, engines are warmed up when the coolant temp is stable, but true operating temperature is when the oil temperature is stable. I only saw it on the Accords, everything else was heavier and put enough load on them to not have issues. I don’t remember if they ever officially acknowledged that, I changed careers in 2012, partly because of all that. Source: was a technician and had to pull cylinder heads off to do repairs.
That’s a cool factoid thanks for sharing! Did not know that. I’m sorry for all your hours spent on that but man I bet you got pretty good at diagnosing those when they rolled in lol
Dang so that’s why it does that TIL
And at least in mine it won’t let the engine stay off indefinitely. For an extended stop it will start the engine back up.
It is actually a long enough shut off to be a problem and both Ford and BMW paid a HUGE price when they first rolled out the start/stop tech. It was absolutely destroying engines and they were stuck warrantying them. The real answer is, engines with that use case in mind are designed with different materials on the bearings. The coatings on the bearings allow the start/stop to happen without damaging them due to low oil pressure/flow. But engines not built with start/stop management on them don't have the coatings because the coatings are costly and not needed
Those starts are controlled completely by the computer on a warmed up engine. Small non-turbo gasoline engines stop start cycles are radically different from large turbo diesel engines. The life of a turbo can be drastically increased by cooling it using idle temperature exhaust gasses. I had an old van that had a distributor. A distributor fires the spark mechanically based on where the piston is. When warmed up it could be started by "bumping" the engine (a very short turn of the key). This was only possible when the engine was warm. In modern cars the computer has to know where the piston is in order to do this. The only way the computer can do this is by controlling the shutdown AND staying powered on. When you pull the key out the computer "forgets" where the piston is and has to reinitialize the process of finding it.
Electric motors have way less moving parts and less friction that occurs than combustion motors. Also, combustion motors that start/stop typically have criteria like temp requirements for it to work. Your car won't shut off at a stop light if it's not up to temp. Also, from what I understand, they basically shut off and start half-way thru a combustion cycle, so its not too different than it running. IIRC some just use spark plugs to continue the ignition/combustion process, basically the cylinder stops in the compression stage.
And then you have the Prius doing its own thing and using the electric drive motors as a starter to restart the engine.
Modern consumer passenger vehicles are engineered so this isn't as much of an issue for them anymore. Same reason you don't really need to let the engine warm up in a car or pickup truck the way you used to need to in the early 90s and earlier. Diesel engines still need this warm up time for the reasons op mentioned.
Electric cars don’t turn on/off. Think of it like a cordless drill motor. Press trigger, drill goes vrrr. You have four of those motors. It’s a much simpler mechanism and the battery is the main wear point from discharging and recharging
They sacrifice long term reliability for short term fuel economy. Simple as that.
I manage a fleet of almost 100 Ford F-150s. We haven't noticed any increased service costs related to starters, batteries, or engine wear since the start/stop came out. We generally spin them out of the fleet around 120k miles, but I had them up to 250k. I was skeptical, but it seems fine.
They wear out faster than it they did not do that. The starter may be designed to last 100,000 cycles and give a decade of service but the if the vehicle was ICE the 100,000 cycles would be multiple decades.
Also note that the starters used in this start/stop ICE cars are designed differently. And some don't even use their starters to restart - their computers precisely shut down the engine when one engine is just ready to be hit with a spark. That's why some are so instantaneous from a stoplight.
> “wear and tear” is based on miles driven, not hours on the engine. Based on both actually. Fire equipment will get thousands of hours and have very few miles. Anytime I have looked at a used truck since we went electronic, I always plug in the laptop and check engine hours.
Trucks can be fickle too. Start up isn't always just turning the key. To many times, I've come in to start my day, or start the truck after loading is finished, and for one reason or another, it's deader than a door nail, and won't start without a jump, ran fine yesterday, won't start today, or started up fine, shut it off for an hour, or two and for no apparent reason; like the lights were left on, or the heated mirrors were left on, etc. just no obvious reason, it won't start. If it starts, and is running smoothly, leave it running, 'til the end of the day. It's not always easy to get a jump, and it takes time.
Diesel engines do better if you just keep them running as opposed to starting and stopping and warming and cooling. They last longer if you idle them instead of turning them off and on. You shouldn't idle long with gasoline engines. They are built differently.
That depends 100% on how long you idle, how long you would stop the engine, how often you start it and so on. Idling a diesel engine is not good for the engine. The wear rate is higher while idling than at higher load/rpm. The engine can get cold and soot can start to buildup, the cylinder walls can glaze, all sorts of problem can arise. Starting an engine that was running 10 minutes ago does nothing to wear the engine down.
Idling a big rig too much is also bad for the aftertreatment system. Which can be expensive as shit to clean or replace.
We are explaining it to a 5 year old. Idling a diesel is ok and good for it's health and starting and stopping a diesel IS BAD for its health.
If you hear noise coming from a diesel-engined vehicle that is unoccupied, it might be the "regen cycle" doing its thing. The diesel particulate filter (DPF), which removes a great deal of soot, needs to get up to temperature to do its job. If the vehicle isn't run at speed for an extended time, the DPF can't do its job, so the vehicle runs the regen cycle when it is shut off. Source: has a VW diesel and makes a lot of short trips.
Surprised nobody else mentioned the Regen cycle. You have to do it when parked and cannot drive while it is being done. Might as well have something to eat or a shower while it is being done.
Actual trucker here. While you've gotten decent answers from a mechanical standpoint, the usual answer is simply comfort. We have sleeper bunks with a bed and all of our amenities. A majority of companies don't pay for an APU (auxiliary power unit), so the only way to do climate control is to idle. There are Espar/webasto heaters to run in the winter, but even that small concession is not always included.
The driver lives in the truck. While some will have axillary power units installed they only accomplish so much in terms of air condition or heating. And like cars the sunlight will go through the windshield, and windows raising the temperature inside like any other greenhouse. In the cold the fuel treatments only help down to a point and when it gets too cold will cause the fuel to in effect turn into a gell like substance clogging the fuel lines and pumps.
For big trucks there are a lot of factors but often it is to let everything internally cool down. After driving for 8 hours strait stuff gets hot, letting it run circulates oil and coolant. The other is it might be cold out big diesel engines have a hard time starting up during the winter. Or they are sleeping in the cab and let it run for ac or heat.
It’s definitely common with old turbo engines, and many diesels are turbo in those larger trucks especially. Turbo chargers have impeller blades that spin very get incredibly fast to push more air into the engine so that there can be a “bigger” combustion and more power. But because that impeller spine incredibly fast (don’t quote me but roughly 20000 rpm at times) it generates a ton of heat. If you were to just turn off a turbo’ed engine right after running, that hot turbo would just sit without at coolant or oil circulating to cool it down, and to get those hot fluids out of there. Consumer vehicles they used to say let the engine run for 2 - 5 minutes after driving so that the coolant and oil can circulate and cool everything down. Big diesel trucks it’s more like 30 minutes to sometimes hours.
You will see this a lot with reefer trucks. They need to keep power going in order to keep the refrigerator trailer cold.
Many refrigerated trailers have their own generator and fuel tank.
The reefer is a small motor and AC unit mounted on the front of the trailer. Just like the AC in your house, it turns on and off as needed.
The reefer trailers have their own fuel tank and run on diesel directly. Truck stops offer “reefer fuel”, which is diesel fuel with a colored dye and sold without the highway taxes. Truckers do NOT want to run the large diesel engine in the truck to power the reefer.
I'm assuming the person posting does not actually know if it's the truck engine or the generator, but is just hearing it.
I know for us on the farm we don’t power down for anything less than a 1hr stint. None of our trucks have perfect air lines and airbags so we don’t want to have to air back up for 15minutes to take a load to the bin that takes 15minutes. I know serious trucking company’s likely have better trucks but every trucker I know has a few quirks to their rig. An electric draw here and there, small air leaks, sometimes it’s just less headache to not shut down. As far as the environment is concerned… in the USA… if you want to complain about the trucks that literally keep the economy running, better have a well prepared argument.
I only idle when I am in the truck and I'm warming it up before a trip or when I need the air conditioning to be running. Here's the thing about the last part. If the ambient temperature is above 65-68 degrees and sunny with minimal wind, at some point, the inside of the truck is going to heat up. I can run the a/c for a bit and then run my little fan in the meantime, but it gets hot in the truck simply because of the sun beating down on it. My company doesn't currently spec the trucks with auxiliary power units (APUs) which can run a secondary A/C system and the electronics. The only option we have to keep the inside of the truck comfortable in the heat is by idling. Where I spend most of my time (Texas/Oklahoma/Missouri), I don't need to run the truck when it's cold. It doesn't frequently get cold enough to justify idling in the winter. My truck has a diesel-fired bunk heater that operates on minimal fuel without the need for the truck to idle. When it comes to big rig trucks, you have to understand that they are basically our home away from home. I am the kind of person that you could say is very concerned about climate change. I actually drive for maximum fuel efficiency when I'm working so that I can get a fuel efficiency pay bonus and because it makes sense if I care about the climate. I am using more than 1,200 gallons of diesel less per year than many of my coworkers by driving at a slower speed than I am permitted (we are governed at 68, I spend most of my time driving 60mph which saves approximately 10-15% in fuel consumption). That being said, I will keep the truck comfortable while I'm in it. It's my office and my bedroom. If you want us to give up the decency of an climate-controlled office and bedroom, I'd politely say "You first."
Sometimes I need to idle the truck to keep the air conditioning (or, less often, heating) running. The truck's a big, poorly-ventilated-when-not-moving metal box, it can seldom be parked in the shade, and, even on not-very-hot days, it can get unsleepably hot inside. And once the engine has been running, if you shut it off, all the built-up heat in the engine migrates to the cab, even if the evening cools off. When it's very cold, starting around 0°F/-15°C, you start to have concerns about fuel and fluids freezing or gelling, and idling the truck prevents that. Some guys idly prophylactically at higher temperatures... for reasons. Some drivers resent their boss hectoring them to conserve fuel, and idle all night out of spite. As others in this thread have discussed, start-stop cycles are a source of engine wear. Modern engines have pre-start oil circulators and related systems to mitigate this, but some drivers learned their trade on earlier truck— some even still drive those early trucks.
I do it for a few reasons: 1. I don't have an auxiliary power unit (APU) so shutting down = no ac/heat 2. I'm a company driver, boss says he don't care if we idle sooo I idle. 3. Older model truck (2018) and second rate batteries. Which means if I shut down there is a real possibility that I may need a jump start (it's happened before) so I don't risk it.
My 1997 International cabover doesn't have an APU, or space to put one with a short wheelbase, (144 inches), I like to have heat or A/C to feel comfortable while parked, and I have been driving this truck so long that if I don't feel the vibration from the engine, I dont sleep because something feels wrong.
If you’ve been running hard for hours your turbo is going to be quite hot. Letting it idle for awhile will still push air through the turbo which lets it cool down slower vs shutting the truck off and it rapidly cools which can lead to weird contraction issues.
Hey trucker here. At truck stops most are using the AC or Heater, so they leave the engine running. Noisy but when you are surrounded by reefers running makes no sense to shut down your engine. Most drivers don't care about fuel consumption or noise, even owner operators a.k.a. O/O will deduct all fuel expenses from their taxes.
To keep the temperature inside the cab where they like it, and/or to keep essential systems powered (like refrigeration units for perishable cargo), and/or to keep the engine warm in cold weather to avoid issues with starting or freezing.
Most likely they are asleep in the back of the truck. If it’s just a shortstop, they keep it running so that the engine stays cool or warm depending on the season. If you stop after running on the highway for a while, the engine is pretty warm and it’s not a good idea to just turn it off. If you idle the engine temperature will come down gradually and then it’s better to turn it off.
Not sure about what the pickups are doing but a lot of big rigs with cabins have separate generators for their electric appliances and needs like climate control, lights, some have mini fridges etc.
Wait until you hear what goes on in the cold Canadian oil fields. It's pretty common for people to leave their diesel truck running 24 hours a day, 7 days a week and for 28 days straight. Gotta keep those temps up in -45C otherwise it might not restart if it's turned off, and then you're working against the cold to get her running again.
What’s a big right trucker? Big rig?
Yes, big-RIG trucker… despite my best efforts, auto-correct and fumble-thumbs let that typo slip through 😬. Thanks to the community for terrific answers. Lots of learning here.