i did a plug change and found oil on the #6 plug. what can cause this and should i be very concerned. it is a 90 xj with 53k original miles



thanks

 

OMG, I had an exact problem or problem like thing , mine is the one that is closest to the windshield , it should be either 1 or 6 .
I was about to post a link on this as well but no need since you did it lol
Well, they told me I needed valve cover gasket , my car runs fine and no misfire but I don't know if it deteriorates

 

If the engine is running well and not misfiring, do not worry about it; it could even have meant the old plug was defective and not firing and burning off deposits.