It seems as if motor oil is leaking in and fouling my spark plugs. Do I need a valve adjustment or is this some other problem?

I have a 1989 190 E 2.6 with 211,000 miles.

Your engine uses hydaulic lfters which dont require adjustment. The problem is more than likely worn valve guide seals and /or worn valve guides.

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Mercedes Benz Master Tech - Retired