Oil on spark-plug threads
 

I'm in the process of changing my plugs and noticed one of the plugs had oil on the threads when I pulled it. The truck doesn't burn any oil and runs like a champ. What could be the cause, and is it anything to be concerned about?

Thanks

Doesn't make a lot of sense that there was oil on spark plugs and yet you're not burning any. Unless it's just so small that you haven't noticed yet. You sure it was oil and not maybe just carbon buildup?

any oil leaks from the valve covers?

Well it doesn't burn any oil significant enough to notice on the dipstick between oil changes. I'm guessing it's a slight leak from the valve covers, I've been using Mobil 1 5w30 ever since the first oil change. Almost 90k on the truck now...

Doesn't oil leak down the valve stems and sit on the back side of the vavles in high milage engines?