This thread seems like a good candidate for a 'sticky', so I thought I would throw in my $.02 worth...
A few weeks back, I decided to do some preventive maintenance on my 10 year old Nissan Xterra...I bought it new and had never changed the [platinum] spark plugs...They seemed to work just fine, but that is what PM is about...The # 1 plug wouldn't budge (aluminum heads!), so after checking the appropriate forum, I bought a spray can of
PB Blaster...Ran the truck for a half hour to warm everything up, sprayed the plug holes, let it sit 4 hours...And started tightening/untightening the # 1 plug...It moved very slightly each way, then suddenly gave a 'screech' and unscrewed right out...After that one, I knew if it 'screeched', it was unscrewing...
I've used Kroil, Marvel Mystery Oil, BreakFree, 3in1 Oil, TapFree, many others...
PB Blaster really impressed me...