Blowby is nasty -- that is why it is routed to the intake on all diesels. Everything up there is oil resistant.

You won't have oil coking on the impeller unless you really get it too hot and just shut off the car without a cooldown, and even then the damage will likely be in the bearings, not the impeller.

Sounds like the amount of oil you have in the turbo is normal. Get a new grommet, though -- you are sucking unfiltered air into the engine, and this is very bad!

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!