Food for thought. My '89 300E has 168,000 miles on the clock. Blew head gasket at 165K. When I got the head off, I too could see original crosshatching on cylinder walls. I have used OEM air filter since I bought the car new. Unless your engine is inhaling rocks, the factory element is more than up to the job.

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Jeff L
1987 300e
1989 300e
1987 BMW 325