help- OIL IN SPARK PLUG AREA

ummm you say the oil was on the top half of the spark plug right? you didnt say if there was oil on the electrode though.
my guess is there was a bad seal around the sparkplug hole. between the valve cover and and head there is absically an o ring to keep oil from leaking out....i had 2 of those seals fail and the spark plug holes would fill up with oil every few weeks. i am willing to bet that is mroe likely the cause if there was only oil on the top half of the plug...

the o-rings are a few bucks each.
when i first discovered oil all all over my sparkplug the entire plug was coated....cause the top half was und 2 inches of oil and when i pulled the plug, obviously all the oil flowed down into the cylinder. i wiped the plugs off, threw them back in, and pulled them again later that day before the oil levels in the sparkplug hole could fill up and it wa sonly the top half...

have you considered a compression test? that will tell you if the piston rings are bad....