Machinist's Workshop magazine tested penetrants for break out torque on rusted 
nuts. 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. The results are as follows; 

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