Why do deisel owners always leave the engine running? Just curious.?

Question

I don't mean that it annoys me. I was just curious as to why. I am talking about going into a store and sleeping in one running and that stuff. I figured it must be technical but not sure. Thanks yall.

Answer 1

Must be because someone (who didn't know what they were talking about) told them to, or it's traditional or some other nonsense reason. It's BAD to let a diesel engine run at low idle for over five minutes! Diesels start up right away, and don't need to be warmed up! People will give all sorts of reasons, none of them valid. It's mainly a matter of misinformation about diesel engines. Low idling can actually damage a diesel engine.

I see a lot of people have misinformation about diesel engines. It doesn't save fuel, it wastes it. It doesn't prevent wear & tear on the engine, it causes it. Need more details?

Diesels pull a full gulp of air on every intake stroke. They have no throttle butterfly like gas engines to restrict air flow for idling. They just change the amount of fuel being fed into the injectors to control speed/torque. If the engine isn’t working hard, it gets just a little fuel, not enough to maintain block temperature, and the intake air is like a big blast of cold air, especially if the turbo isn’t spinning at full compression. Thus the engine cools to below its design operating temperature and you get the high wear factors again.

Idling wastes fuel. It takes about 0.3-0.4 pounds of fuel per hour to produce on HP of output from a diesel. There are 7 pounds of diesel in a gallon. It takes at least 10-15 HP or more to idle a diesel, depending on size, including alternator, compressor, etc. At 0.3 lb/hr, 10 HP = 1/2 gallon of fuel per hour; 20 HP = 1 gallon per hour. At $3/gallon, that’s a lot of bread to be blowing out the stack for no good reason.

Unless folks just like to leave their engines running for all the wrong reasons; no amount of logic or explanation is going to change that!


EDIT:
Tronary's link below substantiates my point.

It is true that truckers will keep the engine idling on a cold night if they don't have a separate heater to heat the cab when they're sleeping. Can't argue with that!

Answer 2

A warm engine being either diesel or gas runs better, but when idling and parked, is still a waste of fuel.

When a gas or diesel engine idles, it cools down a bit which causes the engine to wear faster than one running at full operational temp's. Letting one idle for long periods is harmful to any engine and causes sludge to build inside the engine block.

In extreme cold weather such as here in Alaska, the engines are plugged in to keep warm with electic heaters and such when not running, thus they can be started and warm up to operational temps quicker and minimize wear.

At Prudhoe Bay (Alaska's North Slope) the engines are run 24 hours a day when the temp goes below -20 F. A gasoline truck sitting at the bull rail idling, will need to be refueled at least twice a day with a 20 gallon tank, a diesel truck with the same size tank, will need to be fueled about once every two days. Big difference in fuel consumption, but most folks don't live at -50 degrees and need to keep their engines running.

Turning off a warm engine even at sub zero temps, will still restart with no problems for hours after being shut down due to residual heat left into the engine. The only advantage in freezing climates are, the seat is always warm. So wear warmer clothes.

Answer 3

People used to leave the Diesel engine running to maintain max air in the reservoir for the air brakes. But, that is no longer an issues since today s compressors can build up to operating pressure in 5 minutes. Only corn balls leave a Diesel engine idling while going in to a mini mart to buy goods. 7/19/2015.

Answer 4

While the driver are sleeping they leave them running for the heat or the AC, for driver comfort. These trucks burn about 1 gallon of fuel an hour. These are the trucks that do not have the APUs on them. An APU is an Axilary Power Unit this is to save on the wear and tear on the engine and it uses almost 1/3 of the fuel. But with new ilding laws in most states now it is illegal to idle motre than 5 minutes unles the driver is sleeping inside the bunk.

Answer 5

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Answer 6

if you turn a diesel engine off, the oil in the turbochargers wont circulate properly, and sit there warm and essentially bake,

also, if you or someone you know has ever have a turbocharged car, you/they (shouldnt) drive it immediately without letting it idle for a while, as the oil in the turbos wont be the best, unless you've let it sit for a while before shutting it down, or if you have a system in your car that will leave the motor running after you turn it off and pull the key,

also, it idles at a much lower rpm level, so there isn't much of a concern for gas usage

Answer 7

Hey, this is a nine year old thread but let me tell you about diesels being left on. Any truck being left idling with no driver inside is a danger to the public. Once I saw a parked diesel truck with a trailer but no driver somehow - mystery - jump out of park and roll backwards down a hill. Within less than 100 feet it had jack-knifed and was facing sideways, with the trailer facing downhill, and a huge dent in the back rear where the edge of the trailer had hit the truck while jackknifing. Back rear tire was wrecked, wheel might be damaged. Don't know if the parking brake was on but everything was fine while it was idling so it must have jumped from park to neutral by itself. If a kid had been riding a bicycle on the street or any drivers had been coming there would have been tragedy. If it had actually jumped into reverse or drive it might not have stopped until hitting someone's house.

Answer 8

Actually it is more economical and saves fuel to keep a deisel engine running all the time. Deisel fuel burns much cleaner than regular fuel.

Answer 9

diesel engines are very high compression and they're hard to constantly start and stop. also, it takes more fuel to turn a diesel off and start it again than it does to leave it running for 10 minutes.

Warning: BlueJuliet knows NOTHING of what she's talking about. Anyone who knows anything about diesels know they require warm up time when it's cold because they are compression ignition engines, they depend on heat to run. This person is talking out of her hind end.

Answer 10

deisels have turbo's and with a turbo engine you cant just turn off the engine when its been running and hot. its bad for the turbo it has to cool off and idle before it should shut off. There are people that have modified sports cars and they have to install "turbo timers" which have the cars sit at idle and cool off. while they take the keys out of the ignition and lock the doors and walk away, the car will sit there idling and cool off with the fans or watever and idle normal then shut off on its own. As for semi's they have larger engines and they take longer to cool off.