Recently an article was passed along to me from Machinist Workshop Magazine. They tested some commercially available penetrating oils on a group of nuts & bolts they had scientifically rusted to a uniform degree in a salt water solution. The fasteners were treated with a variety of commercially available penetrants and the measured torque required to loosen them was recorded. The break out torque required for: Nothing = 516 ft. lbs. WD-40 = 238 ft. lbs. PB Blaster = 214 ft. lbs. Liquid Wrench = 127 ft. lbs. Kano Kroil = 106 ft. lbs. 50/50 blend of ATF and Acetone = 50 ft. lbs. edit: It was pointed out that this was a topic a few months ago, so I read through that thread and did notice someone also recommended GM 1052627 heat valve/EGR lube and I have personally used a similar Mopar EGR product for years that works very well but it is definitly more costly then used ATF and Acetone. And a final note on shop safety and penetrating fluids: I was spraying some exhaust bolts on an engine that wasn't running but was warm, when the penetrant hit the bolts it evaporated a bit. The fumes drifted my way and even though I was wearing safety glasses I got some residue in one eye. Flushed the eye for about 20 mins, it remained blurry and irritated so I headed to the emergency room. Brought the can along and the doctor about feel over when he read all the solvents that were in it, long story short, 3 hour eye flush on some hospital machine to get the ph normal in my eye socket.