The subject of penetrating oil is like the topic of your type of
women, beer or NASCAR driver.  People tend to be religiously limited
in their scope.

Machinist's Work Shop magazine of April/May 2007 had an article on
testing a number of the penetrating oils.  Not going into the whole
thing, the bottom line is any oil is better than none.  The author
used a Baldwin compressor meter on a 1200 pound scale.  And all the
items tested were as identical as can be made by man, along with the
simulated years of exposure to a salt solution.

Tested were:

a. none
b. WD-40 @ $.25/oz
c. PB Blaster @ $.35/oz
d. Liquid Wrench @ $.21/oz
e. Kano Kroil @ $.75/oz
f. ATF+Acetone mixture @ $.10/oz (ATF = automatic transmission fluid)

The load needed to remove a dowel pin, put finger-tight in a cold-rolled
low-carbon-steel bar before corrosion, in the above order:

a. 516 pounds
b. 238 pounds
c. 214 pounds
d. 127 pounds
e. 106 pounds
f.  53 pounds

All of them free up rusted parts; most of the cost is in the cans
and advertising.

My other choice is something called "Houdini" that can only be
purchased at a lock shop.  It has a great number of attributes that
work better in locks (30 plus years of locksmithing) along with most
of the other things claimed for the others.  It doesn't contain Teflon,
silicone, grease, oil, graphite, which all tend to cause one problem or
another in locks.

CRC's version of penetrating oil, and oil of wintergreen at the local
druggist shop was a standard penetrating oil used in the military for
aluminum.  It's also for exhaust header bolts and large and small
threaded pipe: heat it up and rub paraffin wax.  It does work more
times than not.  It wicks up into the threads faster and lubes the
threads expanding with the heat.

In my humble opinion, people's problems with WD-40 stem from (1) misuse,
(2) not curing the defects in their cars electrical system when they
only want to believe its moisture in the wiring, (3) parental use,
the choice sort of like the Ford-Chevy-Dodge [preference] thing!

Before the solid state electrical systems in the cars of today, the
wiring for spark plugs was always getting pin holes and leaking
electricity to ground/earth, and other moisture related problems.
Spraying WD-40 on the distributor and wiring would correct the problem
until the next time moisture built up.  Ah, the good ole days... NOT!

And glue in locks is a lot more common than people think.  White
glue or Elmer's glue and super glues are the to most popular to use,
but other stuff that can be squirted into a lock and spread around
among the workings with the insertion of a key are also used.  The
sugar frosting in the small decorating writing tubes are a real pain.
Being sugar, water cleans it out better than oils, but it is hard to
squirt water in a lock <lol>

Glen R. Perye Jr.