Pblaster and Kroil are very similar, both outstanding. Kroil you have to mail-order and PBlaster is in the local auto stores, advantage PBlaster if you want it same-day.
Loctite also has a new product on the market, a freeze-release spray. A pentrating lubricant AND freeze spray, designed to work together in the same can. Since it freezes parts
down instead of heating
them, there's less chance of setting things on fire or detempering them.
I'd sure vote for the PBlaster first. Two or three shots of that, a half hour or hour apart, and even the rock of Gibraltar
would come loose.