This is from the GrassRoots Motorsports board - interesting test.

Rusty bolts? Make your own super rust penetrant!
Suggested by John Brown

So you deal with a lot of rusty nuts? Go down to the hardware store and buy some acetone, a quart of Dexron Mercon and a refillable spray bottle. In the spray bottle mix the ATF and acetone in a 1:1 mixture.

Spray away and get your nuts loose!

Independent testing of penetrating oils using a single steel bar with 1/2”x20 nuts torqued to 50 ft/lbs and treated with a 10% salt water solution that was allowed to rust. Listed are the chemicals and required removal torque.

-None . . . . . . . . 516 pounds
-WD-40  . . . . . . . 238 pounds
-PB Blaster . . . . . 214 pounds
-Liquid Wrench  . . . 127 pounds
-Kano Kroil . . . . . 106 pounds
-ATF-Acetone mix  . .  53 pounds