i removed a spark plug from 1994 E320 and it had oil all over it. The car was running fine, no indication of engine misfiing. I had a red engine light come on after an oxygen sensor fixed it the first instance. i washed the engine and then it came back on a couple of days later. A post said water gets in spark plugs and stays there for some reason causing engine light. I was checking this when i noted all of this (fresh) oil dripping off the plug when I pulled it out.Bosch platinum +4 R3. I am going to get new Bosch copper plugs. Still do not know what is best recommendation for plugs.

I hope none of the other plug holes have oil.