Oil on my spark plug threads

I changed my plugs yesterday to a new set of Pulstar Idg1h plugs. They work very well, however, the factory plugs I pulled out have oil on the threads. The spark plug tips were a normal toasty brown. The oil is only on the threads. I haven't had any luck finding anything on this in this forum pertaining to this issue (I could have missed something). Is anyone else having this issue? I have about 125,600 miles in it. Any help would be appreciated.

 

More than likely the valve cover gaskets are leaking ( spark plug tube gaskets )

 

I had a feeling, but wanted another opinion. Thanks!

 

It’s definitely the spark plug tube seal portion of the valve cover gaskets. The oil sits in on top but as you pull the plug it runs down onto the threads.

 

https://www.4runners.com/threads/a-...in-a-4runner-limited.8250/page-21#post-233344