Today I was doing a tuneup on my car, '94 5S-FE. As I removed the spark plugs, numbers 1 and 2 were fine, but 3 and 4 each had oil on the top of them, a little bit of oil was on the threads but I figured that was just from it leaking down while I was unscrewing the plugs. Is this a bad valve cover gasket, or something else? The engine runs great, it has high mileage but it hasn't given me any problems. It doesn't burn any oil either, as far as I can tell.

Spark plug tube gaskets.