Copied from another site but interesting...
Penetrating Oils
Machinist's Workshop recently published some information on various penetrating oils. The magazine reports they tested penetrates for break out torque on rusted nuts.
Below listed, a subjective test was made of all the popular penetrates, with the control being the torque required to remove the nut from a "scientifically rusted" environment.
Average torque load to loosen
No Oil used ................... 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 is a "home brew" mix of 50 - 50 automatic transmission fluid and acetone. Note this "home brew" released bolts 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 almost as good as Kroil for 20% of the price.
ATF-Acetone mix is best, but you can also use ATF and lacquer thinner in a 50-50 mix. (ATF=Automatic Transmission Fluid)