Penetrating Oils Compared

Machinist's Workshop magazine is reported to have tested penetrants for break
out torque on rusted nuts. (I'm waiting for vevrification)

Significant results! 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 - 50 automatic transmission fluid and acetone.

Note the "home brew" was better than any commercial product in this one particular test. A local machinist group mixed up a batch and 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.

Rocket Chemical Company and its staff of three set out to create a line of rust-prevention solvents and degreasers for use in the aerospace industry.

Working in a small lab in San Diego, California, it took them 40 attempts to get the water displacing formula worked out. But they must have been really good, because the original secret formula for WD-40® -which stands for Water Displacement perfected on the 40th try—is still in use today.

https://www.wd40.com/cool-stuff/history