I remember reading years ago of the importance to allow time for turbo units (both gasoline and diesel) to cool down from operating tempertatures because of the 'heat soak' effect. In an '86 300SDL, does this hold any more or less true? Has Merecedes made some special provisions most people are unaware of that will protect the turbo from oil coking in the bearing? I have heard that some manufactures employ some sort of oil siphon that continues to circulate oil through the turbo bearing after the engine has been shut down.
On a recent cross country trip, the approach I took on this issue was to allow the engine to idle during all quick stops without shutting it down (refuelling and rest stop breaks) and when shutdown was necessary for longer stops (overnight stays and restaurant visits) the engine was allowed to idle for at least five minutes prior to shut down. Is this an approach I should continue? Any modifications to these practices? Is oil dilution at idle as much an issue with diesels as with gasoline engines? I really don't relish the thought of turbo replacement and since the car has about 155K miles, I would like to think that, in Mercedes terms, I'm only half way there. Thanks for your input.