oil on spark plug thread

Changed out my plugs last night. I installed the last set 30k miles ago. All of the old ones looked pretty good. Dry etc. The plug on the driver's side, closest to the firewall (away from the oil fill spout) had a dry spark end which looked normal, no additional carbon etc. Yet, it had oil on the threads. No oil has leaked, dripped, been poured, etc. into the hole. I inspected the hole for the spark plug and there was no dirt or oil. So the oil must have come from the the cylinder? But the end of the plug was dry and not any different from the others. Anyone have any explanations. Something to worry about or no big deal? Engine sounds fine and runs fine. Mileage had been going down a bit. I was hoping new plugs would bring it back up.


Thanks
Yamabiker

 

Is it oil or maybe anti-seize ?

 

This might help.

 

It seems to be normal on the drivers side closest to the plug....your not the first one to notice that when people change there plugs...its happened to me first hand with my 05' and my 11' I installed my supercharger at 11,000 miles on my 11' and had same thing...oil on the plug so it seems to be a characteristic of the 4.0L

 

Thanks for digging up that thread Lucario Runner. My #6 plug looked similar to those pictures. Makes sense too since the sparky end is clean.

Yamabiker