Mark :
PMFJI, but yes, API GL-5 is a standard for gear lubricant, much like SH for
motor oil and DOT-5 for brake fluid. It specifies things like film
strength, temperature resistance (both high & low), compatibility, etc. It
does not specify actual ingredients, hence Redline (and others) can market
a pure synthetic GL-5 while other people market petroleum based GL-5.
Actually, a little web surfing turned up several surprising facts which
cast some doubts on the GL-4 vs GL-5 discussion :
1) Some companies market the same oil as both GL-4 and GL-5. Actually, it
appears that most GL-5 oils will meet GL-4 specs, but some companies don't
bother to run the older test. For instance, Amsoil Series 2000 "meets or
exceeds ... GL-2 through GL-5".
2) The standard for compatibility with copper (the primary ingredient in
brass, which is an alloy of copper and zinc) is _tougher_ for GL-5 than
GL-4. I didn't look up the test procedure (ASTM D 130), but GL-4 only has
to pass for 1 hour, while GL-5 has to pass for 3 hours (both at 250F).
(For those who want to repeat the test at home, it involves immersing a
bare copper strip in heated oil for the specified time. The strip is then
removed, cleaned, and examined for corrosion/discoloration.)
Apparently, the real issue is sulfur (or sulphur) content, which improves
the EP characteristics of conventional oil (and gives conventional gear oil
that distinctive smell), but which can separate into corrosive compounds
(like sulfuric acid !) at high temperatures.
Lubrizol has a nice web page, with lots of background information on gear
and transmission oils. http://www.lubrizol.com/referencelibrary/lubtheory
Much of it is oriented towards heavy equipment, but they do discuss
passenger cars as well. They have the definitions of GL-4 and GL-5 posted.
Randall
On Monday, March 01, 1999 8:17 AM, Mark Gendron
[SMTP:mister_toad@email.msn.com] wrote:
>
> > From: Tony Rhodes <ARhodes@compuserve.com>
> > Subject: OD gear oil- info from Redline
> >
> > GL-5 brass corrosion. Only a problem at elevated temperature (300
> degrees), but
> > the redline GL-5 does NOT cause corrosion of brass at anytemp. BUT it
will
> > discolor the brass at high temps.
>
> You seem to have made two contradictory statements about GL-5. This makes
> sense
> if GL-5 is a generic name, rather than a Redline trademark ("Non-Redline
> GL-5
> damages brass at high temps, Redline-brand GL-5 does not.")
>
> Can you clarify this?
>
>
>
>
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