Oil on single spark plug

I was changing my spark plugs on my 2010 Sequioa and the second from the front on the passenger side (either 4 or 6, not sure which) was coated in fresh oil. All of the other plugs were dry and seem to have burned normally. From what I've read, I unfortunately believe this to be either the valve stem seals or the piston rings. Is there anything else that could cause this or would you agree with my diagnosis?

 

Oil is on the combustion side or on the white porcelain?

 

On the combustion side. I also had oil in the air intake behind the MAF so I replaced the PCV valve. I'm going to check the plug that had oil on it in a week to see if anything has changed.

 

If you have oil in the intake it is comming from your pcv system for sure. Have you notticed oil comsuption and blue smoke?

 

No noticeable smoke but it's definitely consuming oil at a slow rate. Normally about a quarter or so between oil changes.

 

Update us with your result next week! Hope the pcv valve was your issue

 

See here.
https://forum.ih8mud.com/threads/oil-on-spark-plug-threads.1327761/