By January 21, 2013 2 Comments Read More →

Oil On Spark Plugs

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oil on spark plugsReader Question

I am doing a tune up on my car and noticed I have oil on my spark plugs. What should I do about it and what causes this to happen?

Danny D.


Hi Danny,

Oil on the spark plugs tells me there is an internal oil leak inside the engine. You could have a valve problem in the cylinder head which is leaking oil past the valve stem seals, or you could have a more serious problem like worn out piston rings.

You might want to try using a thicker weight of engine oil and or an oil additive like Engine Restore, to thicken and reduce your oil consumption. Also make sure the PCV (positive crankcase ventilation) system is working and replace the PCV valve if you have one.

Posted in: Tune Up Costs

2 Comments on "Oil On Spark Plugs"

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  1. Allie says:

    Hi Mr Davis,
    1989 Mercedes 300 ce
    Initially only one spark plug used to get foiled by oil gump
    I had the cylinder head redone including valve stem seals and valves replaced now all six plugs are oil gumped within one week
    or after 50 kilometers
    please advise
    Kind regards

    • Austin Davis says:

      I would assume you have internal wear on the piston rings and cylinder walls causing loss of compression and “blow by” causing the oil to get on the spark plugs. I would do a compression test on all cylinders to verify that. If that is the case, not much you can do except overhaul the engine or replace it. You CAN help slow down the oil consumption by using thicker weight engine oil like straight 50 weight oil (castrol makes a good one) and using an oil additive like We used to use “anti foulers” which screw onto the spark plugs to help keep oil off the plugs….not really recommended for computer control vehicles like yours….but you don’t have too many choices either.

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