2002 Volkswagen Jetta sprk plugs

Hello -

If you are talking about when you remove a plug there is oil on the end of it then oil fouled spark plug Heavy black deposits with an oily appearance. These are the result of oil entering in the combustion chamber, probably past worn valve guides, guide seals or rings. Switching to a hotter plug may help prolong plug life somewhat, but no spark plug will survive long under such conditions. The only permanent cure to this condition is to fix the oil consumption problem.