Forwarding a prior e:mail on the subject (though heating to cherry red is the final method like Larry above suggests):
Machinist's Workshop V20 number 2, April/May 2007, page 35
Article: “Testing Penetrating oils”
This reports a test of penetrating oils where they measured
the force required to loosen rusty test devices. The
details reported here were validated by the original
article author. He also added some details on the methods.
You must buy the issue if you want to see how they did the
test. The back issue is available for purchase.
The table below extracts the results table The lower the
number of pounds the better. Interesting that a simple mix
of acetone and power steering fluid (PSF) works the best!
Penetrating oil - Average load -Price per fluid ounce
None ...............516 pounds -- 0
WD-40 ..............238 pounds --$0.25
PB Blaster..........214 pounds --$0.35
Liquid Wrench ......127 pounds --$0.21
Kano Kroil .........106 pounds --$0.75
PSF-Acetone mix ....53 pounds ---$0.10 (50/50 mix)
Note from original article author:
1) These are loads required to free the test piece after
8 hours of immersion in penetrating oil. This is
probably not representative of a quick squirt just
before a wrench is applied.
2) The original article incorrectly stated Automatic Transmission Fluid was used in the DIY.
mix. Power Steering Fluid was actually used.
