I changed the spark plugs and I found oil on the spark plugs.Why?
My car has 138000 miles.
My car has an automatic transmission.
Oil can leak into the combustion chamber from either the piston rings or through the valve guides (past the valve stem oil seals). Of course once oil is there, the spark plug can get contaminated. If the leak is past worn out valve stem oil seals, that is not too hard to resolve as the rubber seals are replaceable. Leaky piston rings are another matter. Such is best resolved by a complete engine overhaul as if the rings leak there will undoubtedly be worn parts elsewhere. To have the leak evaluated, the recommended service is an oil leak diagnostic. If you request that service, the responding certified mechanic will get your concerns addressed and recommend a repair strategy for you. If you have further questions or concerns, do not hesitate to re-contact YourMechanic as we are always here to help you.
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