Poor oil drainback can also cause oil to get into the clean air supply line and hence into the air filter, and if you are getting more blowby than the idle air uses, it will get misted into the intake.

Could easily be valve guide seals, which are due for replacement at 200,000 miles anyway. Normal time to first valve job is about 250,000 miles, so start saving your pennies.

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!