Help me understand why big honkin diesel pickup drvrs leave the engine running while sitting in a parking lot?

cheaper to let it run than to restart it.

Diesels aren't like gasoline engines. They have a turbo charger that runs off HOT exhaust gases. Exhaust gases are VERY hot which causes the turbo to get VERY hot. If a driver, after a hard run, pulls into a parking spot and shuts the engine down, the turbo charger will also stop, cool down slowly allowing the center shaft to sag. If this happens, the driver just bought himself a new VERY costly turbo charger. The cool down period usually takes around 10-15 minutes. This is why you may see him/her sitting in the cab smoking a cigarette.

The driver may just taking a quick break and the AC sure feels good when it is 100 degrees out and the engine is putting out heat also. Don't be so hard on them. Truck driving is a lonely, hard but rewarding job. Pops

I have thought about this also. Here is just a guess. A large diesel engine holds a very large quantity of oil in the crankcase. Whenever you stop the engine it begins to cool and moisture in the air inside the engine condenses. The moisture mixes with burned diesel by products and creates a mild acid that pollutes the oil leading to needing a premature oil change. That can be very expensive.

Actually, I drive a diesel, so I can offer some insight for you.... It actually uses and burns more gas to stop and restart the engine than it does to leave it running, and if the truck is in good shape, it burns and emmitts the least amount of fumes when it's sitting in idle. Also, and this is true for any vehicle, it adds much more wear and tear to the enging with constant stopping and re-starting..... Hope this helps!!!!

Diesel engines are designed to run at idle speed better than gasoline engines. Also it is harder on a diesel engine during start up hence it is cheaper for the owner to leave the vehicle idling than it is to turn off and start back up a couple of minutes later.

a diesel truck engine needs the high compression ratio to make it run properly, around 20.1:1, where a conventiontial gas engine is around 8.5:1.Both engines use the expansion of the exhaust gases to seal therings to cylinder wall. In other words, the expanding gases push down on the top and th back of the rings making a proper seal. Constantly starting and stopping an engine makes the rings stick in the pistons leading to premaure engine failure.

The new diesel fuel wont make it a good idea to run all the time,The new fuel lacks lubrication, most manufacturers no longer advise long idle times as fuel dilution into the crankcase ruins the lubrication of the oil.I work on detriot diesels alot and the main problem is oil dilution on bearing wear.we get some bearing wear results on our oil lab numbers.

Because odd as it may sound it's actually more fuel efficient to leave the motor running than to shut it off and start it back up. Plus on many pieces of equipment they have to be started constantly due to the batteries used on them. German tanks during WW2 had to be turned over and run every 4 hours.

a diesel is a compression ignition engine and is way more efficient at temperature than when cold , also the turbos wear faster in start stop situations

i own a repair shop,and i do diesel work,and its just as cheap to leave it running than it ts to re-start it, i have left them running here at the shop,for hours at a time just to see if they was going to be alright,but this is the main reason for leaving them running,this and also in the winter it keep the cab area warm for the driver,good luck i hope this help,s.

They are left running because it is more efficient to do so than to re-start it every time they want to leave.Diesel engines have a glo plug that takes some time to warm up,before you can start them,so it is much easier to just leave them running.