I saw a sort of a modern miracle the other night. I set out to change the oil in an 05 Dodge truck I've bought... Some idiot had turned the oil drain plug in with an impact tool and the next person who tried to take it off with a wrench had totally stripped it, .5" wrench wouldn't go on and 13mm just turned...
Despite age and back problems I'm still stronger than most people but, as tight as I could get a vice-grips on the thing it still wouldn't turn, that was just going to strip the thing worse. WD-40 would not have touched this one.
Neighbor had a can of Aerokroil handy; just sprayed the drain plug, waited fifteen or twenty seconds, and turned the thing off with a vice grips as if it wasn't a problem.
He tells me the stuff gets down to a molecular level i.e. flows into things something like one millionth of an inch wide. I've called all of my mechanic-type friends and none had heard of this previously.