I have shamelessly copied this from another site: *Don't forget the April 2007 "Machinist's Workshop" magazine comparison test.* ** *They arranged a subjective test of all the popular penetrants with the control being the torque required to remove the nut from a "scientifically rusted" environment.* ** *Penetrating oil ..... Average load* None ..................... 516 pounds WD-40 .................. 238 pounds PB Blaster ............. 214 pounds Liquid Wrench ..... 127 pounds Kano Kroil ............ 106 pounds ATF-Acetone mix....53 pounds *The ATF-Acetone mix was a "home brew" mix of 50% acetone - 50% automatic transmission fluid.* *Note the "home brew" was better than any commercial product in this one particular test. Our local machinist group mixed up a batch and we all now use it with equally good results. Note also that "Liquid Wrench" is about as good as "Kroil" for about 20% of the price. * What is this? Replacing marketing hype and the way it has always been done with test data? They didn't test spray silicone oil. I like it as a non gumming lube, and go ahead and use the same thing as penetrating oil. Heat and quench works. For a time I worked in a brake shop. We salvaged many calipers with a broken bleed screw with what the owner called the heat wrench. It is much easier to reach for the torch before you bust something off. Out in the field, a little gas may help. A good hammering does too. I usually give things a squirt of silicone and then hammer away.