I use paper filters in both my MB's BUT I have a lot of customers that use K&N filters. One comes to mind that may shed some light on the subject. He installed a K&N in a new 94 Chevy 1500 with a 5.0L engine. So far, he has only been able to get about 350,000 miles on the truck. It still uses no oil, runs good and has no engine problems. He also has it serviced every 3K miles, keeps the transmission serviced every 30K, and in general keeps the truck in good shape.
The only engine problems we see now are caused by poor maintaince, not the wrong air filter.
Moral to the story is.."Keep it serviced".

Paul

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84 500 SEL (307,xxx miles)