This subject gets beat to death. Been a mechanic for well over 30 years. Never and I repeat Never has even one manufacturer ever used lube of any sort on any spark plug thread ever...
I think there may be more than a few phord owners who wished that phord had used something on their spark plugs.
Yep, carbon build up on threads and crappy Autolite 2-piece plugs.
PIA changing those, lucky to see chatter on Mustang forum, only broke 2, and that was after only 30k.
Nickel high temp on everything now.
