Oil found on spark plug threads.

[shiwei]

Hi guys.
I did my compression test today on my 2005 Mazda 3s, 4 cylinder with 56K miles.
I started removing my passenger side spark plug, but found oil on the spark plug threads. It smells like engine oil, but I am not quite sure. Other 3 spark plugs are quite dry and clean.

BTY, I changed my engine oil by myself, and the can has no burning oil problem.

What are the possible reasons for the oil on the spark? It’s quite weird this plug has oil while others are dry.

Topic

[David]

Sometimes the seals at the bottom of the spark plug tubes go hard and leak.

[sam priem]

there are 4 seals that go around the plugs, 1 for each plug. they work with the main valve cover gasket to keep oil inside the valve cover. you would have to pull the valve cover off which, if i remember right, isnt too bad of a job (im assuming 2.3L?) to replace the main valve cover gasket and the 4 smaller gaskets for the plugs.

[Bluesnut]

Hopefully the plug well seal is leaking on the valve cover. If not, the next possibility is far more serious. That means a piston ring issue.

A plug well seal leaking should mean oil on the plug boot and plug body also.

[Author]

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