what would make the oil to get on # 3 plugs on a 02 c320 benz
Which part of the plug? if its the top then it could be a bad valve cover gasket, if its the bottom of the plug it could be much difficult to determin. Bottom of the plu could mean bad rings, ect.
Are you sure it's oil and not just an old blackened plug wiv a bit of unburnt fuel?
If the oil is on the outside of the plug , then it could be the valve cover gasket. Simple fix. either tighten the valve cover bolts (normally after awhile when the gasket gets hard and brittle they shrink and you may need to torque down the valve cover to stop any little leaks that may start) wost case you buy a new valve cover gasket. Now, if you are detecting oil on the plug when you take the plug out and inspect the tip, you have a more serious problem. Does the car spew white smoke when you accelerate? Then, an engine rebuild is in order.
Looking for a Used C-Class in your area?
CarGurus has 23,136 nationwide C-Class listings starting at $1,995.
Search Mercedes-Benz C-Class Questions
Mercedes-Benz C-Class Experts