My 06 cobalt just rolled over 135K this week. I've replaced the serpentine belt and plugs myself so far. I noticed the drivers side plug had oil on the threads, none on the electrode though. The others were clean. Do i need a valve cover gasket set? I like to do things myself. Is this pretty easy? Anything else I should consider working on? The car seems to be running great. Drive it roughly 95 miles a day. Any ideas would be great. Thanks!

 

Sounds like a valve cover gasket. I changed the fuel filter at 100k. Very easy it's in the back above the rear beam.