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?

 

For one those spark plugs are shot, I bet your MPG's sucked. And yes, it is a good a good sign of worn rings, Also lots of exhaust smoke and even bad idle. Check and see

 

actually... no smoke, and perfect idle.

Haven't had a chance to check the MPGs yet, I just bought it yesterday.

 

If they have been taken out before, then the PO probably oiled the thread when put back in.

 

oh well, bad plugs will eat MPG's, But like Evan said, if they have been taken out then they could have gotten oiled. Your rings are fine, I wouldn't be worried at 120K