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I have been told to never try to remove plugs from a hot engine. It should be cold.
Try the PB Blaster or WD40 trick. It worked for me. The oil easily
penetrated the threads and made removal a breeze.
I agree about pulling the plugs when the engine is cold, but I have no idea how ANY kind of lubricant would help the removal of the plugs, UNLESS the plug was already somewhat loose before the lube was applied.
The plugs in an LS engine seal to the head by a tapered seat, which is part of the spark plug, and ABOVE the threads. If that plug is installed properly, that seal of that tapered seat is containing the pressure of the combustion chamber, so WD-40 certainly isn't going to get past it......