Hello, I am Kevin and am new to the forum and I am seeking assistance to trouble-shoot and repair the cause.

I have a W211, 2009 E350 Mercedes-Benz, On the right side passenger (exhaust) my spark plugs have deposits of oil on them.

Are there seals that need to be replaced?

I appreciate and grateful for your help.

Thank you

How many miles on the car. Oil on the spark plugs could be a sign of worn oil control piston rings. I would recommend that you have a cylinder leak down test performed on the cylinders in question. The test will inject compressed air into the cylinder and if you can feel or hear air escaping from the port where oil is normally added to the engine that is normally a sign of worn or broken oil rings on the piston. The other possibility is worn valve stem guide seals. If after idling the engine and then accelerating you see blue smoke out of the exhaust pipe that is a sign of worn valve stem seals. You may also want to install new spark plugs, drive the car a few thousand miles and check the plugs for oil again. The valve stem seals are the cheaper fix but still will cost $$ to have repaired.

Post a picture of you can. Where exactly is the oil? Is it on the ceramic part by the plug boot OR is it on the part that is in the combustion chamber?

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If the oil is on the ceramic part of the spark plug the problem may be a simple valve cover gasket leak.