I have an '86 K10 Suburban. Put a new GM "Target" crate engine in about about 60k miles ago. Never had any spark plug issues until started using Mobil1 oil at about 40k miles. Keep in mind this is an old technology, carbureted, non-computerized engine. Noticed the #8 spark plug started getting oil deposits and fouling out. Would foul out even after as few as 300 miles. This was especially noticeable after pulling a trailer. I've decided the valve stem seals are probably letting the "thinner" synthectic oil by. I've gone back to conventional 10w30 Valvoline that I've used for years. So far so good, but only about 200 miles so far.
Does anyone any thoughts on this? Will the problem rectify itself or will I still have to change valve seals?
All thoughts and comments will be greatly apprecitated.
rcreechssr