I just wanna know if an oily spark plug means that i should have it overhauled? i just had it overhauled 4th quarter last year... or should it be considered "back job"? My car is Toyota Corolla 95 Big Body... 3 of the 4 spark plugs are covered with oil... only one is colored rusty brown... the mechanic told me that it was only dirty and no problem at all... i am kinda hesitant about that... oily sparkplug means a problem in piston ring or other parts...