Jmartin957 has it right! "ATF & acetone, Liquid Wrench, PB B'laster, WD-40 all work to some extent, but in my experience they all fall short of the real king of the hill - Kroil." It's been my go-to unsticker for decades. Yes, it is expensive, but a few ounce can is still affordable to have in the back of your kit. When all the other tricks fail, go to Kroil.