The post highway run idle period has nothing to do with oiling a spinning turbo, it has to do with the whitehot turbine dumping all that heat into the main shaft and bearing. The excess heat and no cooling from oil circulation will result in the oil remaining in the bearings baking into scaly carbonaceous crud that will seize and/or grind away at the bearing, ruining the turbo.

Turbochargers run at speeds up to 100,000 rpm, so a special floating bearing is required. Coked oil isn't a good thing.

MB also already has a turbo "shutoff", at least on the 601/602/603 and later turbodiesels called an air bypass valve -- vents the boost back into the intake side. This was partially to make the trap oxidizer work better, and to lower emissions by increasing boost more slowly, but also to give better milage on the highway by reducing boost in light load cruise. Seems to have worked, since I get better milage with it connected than disconnected!

It did, however, also cause serious turbo lag sometimes, and cruise control surge under some condtions, which is why I disconnected it.

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!