'82 300D turbo questions

Idling after driving won't hurt it but is not necessary. Gasoline engines have hotter exhaust than diesels so idling them after driving is an excellent idea but diesels' relatively lower exhaust temperature are benign on turbos. Turbos on our diesels usually last the life of the engine's other major components - without special treatment.

The best answer I've seen to this not-uncommon question is "no you don't need to but if you don't and your neighbor does your neighbors car might last a bit longer".

Keep in mind that the factory doesn't want the car to idle for 5 minutes. That long or longer and they want you to shut if off to prevent carbon from accumulating in the prechambers. So, two mainutes tops I'd suggest.

This is kind of ridiculous, as obviously the car is going to be idling for longer then 2 minutes when it is in service.

Which is why howay driven cars have much cleaner engines than city driven cars and why running some diesel purge through them helps.

Rediculous or not MB says if it idles for more than 5 minutes shut it off and they've said this for years.

Having said that there are people that let their diesels run overnight in extremely cold situations, but you do need then to deal with the commensurate carbon buildup problems - diesel purge.

Cooling down the turbo isn't the reason that idling the engine prior to shutting it off is sometimes recommended. If the material in the turbocharger were all that sensitive to high temperatures, it wouldn't have been used in that application in the first place.

Rather, the reason is to ensure that the bearings have adequate oil flow as the turbo spins down. The only time I bother to do this is when I've been driving fairly fast and then park the car without a transitional period of slower driving, such as when I pull into a freeway rest area.

Geoff

This has been discussed at some length and the consensus seemed to be if you use synthetic oil it'll hold up to the high temepratures found in turbo bearings and you can just shut it down. But, if you use dino juice it probably doesnt hurt to let it run a few minutes to cool down a bit.