I am on a machinist group and know many of you come across this problem of rusted bolts, nuts, etc.
Some of you might appreciate this. Machinist's Workshop magazine
tested penetrants for break out torque on rusted nuts. They are below,
as forwarded by an ex-student and professional machinist, Bud Baker.
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. 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.