Spark Plugs Covered in Oil

Pulling a spark plug and finding it dripping with oil is a clear sign something is leaking where it shouldn't be. The good news: it's usually fixable.

Oil on spark plugs comes from one of two places. If the oil is on the outside of the plug — in the spark plug well or tube — the valve cover gasket or spark plug tube seals are leaking. These seals sit where the spark plug tube passes through the valve cover, and when they fail, oil fills the spark plug well from above. If the oil is on the electrode and firing tip of the plug (the business end inside the cylinder), oil is getting into the combustion chamber through worn valve stem seals or piston rings.

Oil in the spark plug wells is the more common and less serious issue. It can cause misfires because oil is a poor conductor of electricity, and it can degrade the ignition coil boots that sit on top of the plugs. The fix is replacing the valve cover gasket set, which includes the tube seals. This is a bread-and-butter repair. Oil on the firing end of the plug indicates internal engine consumption — a deeper issue involving valve seals or ring wear that's more involved to repair.

Valve cover gaskets and spark plug tube seals are a job our mobile mechanic team in Jacksonville, FL does all the time in customers' driveways. We'll replace the gaskets, clean the oil out of the plug wells, inspect or replace the spark plugs, and check the ignition coils for damage. It's typically a 2-3 hour job depending on the engine. Call (904) 788-7272 — we'll bring everything needed.