The stock oil separator is a centrifugal one (the blowby spins round in the can, throwing the oil onto the sides). I suppose you could put mesh in it, but I would suggest a stainless steel scrubbing pad instead of a 3M scrub pad. It will remove as much oil, but the oil will drain out much better, and it will be cleanable. The scrub pad may not tolerate oil very well. If it gets packed down, it will go solid with oil and you risk pressurizing the crankcase. Won't cause any trouble, but the blowby will all go out the dipstick instead. You probably aren't going to increase the efficiency much by putting mesh in there anyway.

Send the blowby in behind the air filter, or it will fill up with oil pretty quick, and once oily, will prevent air flow.

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!