[Rharp]

Hey everyone,
Yesterday I changed the plugs in my Chevelle and there was oil on all 8, but only on the threads. Car seems to run fine, I do notice what I think is steam (not smoke) coming from the passenger side exhaust. I don't drive the car enough to be able to say if it burns oil or not.
I'm stumped!!!
What would cause oil to be just on the threads, and no where else?
Opinions please!!!!!!