These turbos are oil cooled, so if you shut the engine off with the turbo hot you can fry the oil since it stops moving. The resulting carbon (coke) on the bearings is VERY hard and wears them out.

Interstate rest stops are hell on turbos -- you are flying along, pull of, and within seconds are at a full stop. The turbine is still red hot (or hotter in the mountains!), and if you just shut right off, you have trouble. It wont' be turning fast, just hot.

A minute or two idle time will cool it off enough to be safe, especially if you use synthetic oil, as I strongly recommend with turbos. A couple or three blocks of city or suburban traffic is equivalent to the minute or two of idle, but if you want to play it safe, get in the habit of letting the car idle a bit before shutting off, then you won't forget on the interstate!

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!