Originally Posted by fireandrainksm
Could the oil buildup be from an oil change missing the oil filler? Since it is on that side.
It could be. It dripped on the coil from somewhere. The oil expanded the rubber seal and allowed more oil to fill the well. My daughter bought the truck used and has the dealer or a local shop change the oil so it's hard to tell what happened.
I'm adding the update for those searchers that experience a similar problem. I didn't find anything about oil in a spark plug well when I searched.
BTW: we bought a eBay coil for under $15 as a replacement. The original coil still worked but the well seal expanded and the poly spark plug insulator came off due to the oil.