Just bought a 2004 Ranger Edge (3.0) with 120k miles on the clock. Decided to change the plugs tonight since I have no idea when or if they have ever been changed. I found that all 6 had some oil residue on the threads. The tips didn't seem to have any on it though. Is this normal? Other cars I have changed plugs on in the past didn't look this way, and I've heard that oil on them can be signs of worn piston rings.
Having said that, the valve cover gaskets both leak a little (will change them when I get time). Maybe some just leaked down into the spark plug holes?