Date:         Fri, 5 Oct 2007 14:20:54 -0400
Reply-To:     Mike S <mikes@FLATSURFACE.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Mike S <mikes@FLATSURFACE.COM>
Subject:      Re: Mobil I ... negative..(from digest)
Comments: To: rubatoguy@COMCAST.NET
In-Reply-To:  <100520071739.5695.470676DD00001B970000163F2213539653979A09
              019B0E0D9A9D@comcast.net>
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At 01:39 PM 10/5/2007, Todd Last wrote...
>No, but you don't want to use it if it has a GL-5 rating.  (Alledgedly
>the additive in GL-5 attacks the transmission synchros)

If it also carries an MT-1 rating, it is actually tested for yellow
metal (synchros are copper alloys) compatibility to a higher standard
than a GL-4.

GL-4 requires ASTM D-130 copper strip rating of 3B max. (after 1 h @
121.1C).

GL-5 does not require the ASTM D-130 test for stability in the presence
of copper and copper alloys.

MT-1 lubricants meet an ASTM D 130 requirement of 2A max. (after 3 h @
121.1C). This is a more stringent requirement than that for GL-4.

The copper strip rating is determined by ASTM D-130 which is designed
to assess the relative degree of corrosivity of the sulphur compounds
contained in a petroleum product. The test is carried out by immersing
a polished copper strip in a given quantity of sample, heating at a
temperature and for a time characteristic of the material and comparing
the copper strip after it has been washed and dried with the ASTM
Copper Strip Corrosion Standards.

As far as wear capabilities the required testing is:
API GL-4, CRC L-20
API GL-5, CRC L-37
API MT-1, No requirement

These tests are for determining load-carrying, wear, and
extreme-pressure characteristics of gear lubricants in axles under
conditions of high-speed low-torque operation, followed by low-speed
high-torque operation. L-37 is a more severe test.

Tests for thermal & oxidation stability/component cleanliness:
API GL-4, No requirement
API GL-5, L-60-1
API MT-1, L-60-1

There are multiple other performance tests, all of which require a
GL-5/MT-1 gear oil to perform better than a GL-4.

The only area of concern is with regard to friction modifiers, which
can determine how well the transmission shifts. Without a friction
modifier, the oil may actually be too slippery to spin up the synchros
fast enough for good shifts. This will typically not be a problem on a
Vanagon, unless someone is racing theirs and trying to speed-shift.

Having said that, I use Redline MT-90, a synthetic GL-4 gear oil, as
recommended by Daryl of AATransaxle.