Best trans oil choice

Bernie Benz b.benz at
Mon Oct 17 11:09:45 EDT 2005

Eric, Brett,

Brass compatibility IS NOT the principle reason for not using GL-5 in a
syncromesh transmission.  GL-5 is an extreme pressure lubricant necessary
for Hypoid gearing such as the rear end.  As such, it will render the
syncros of a syncromesh tranny less or ineffective, but won't hurt anything.
Thus the GL-4 requirement.


> From: Eric_R_Kissell at
> Date: Mon, 17 Oct 2005 08:29:21 -0400
> To: Brett Dikeman <brett at>
>>> What is the consensus on the proper oil to use for the
>>> transmission in the 200tq?  How about the rear end?
> <brett at> responded:
>> Stock VW/Audi fluid.  Amsoil also makes a GL5 that IS compatible with
>> VW, Porsche, and Audi transmissions.
>> If you consider any GL5 rated fluid, triple check with the
>> manufacturer that it is compatible with VW/Audi transmissions and is
>> brass syncro safe.  It used to be that all GL5 fluids were NOT, and
>> now several (including Amsoil) are; an additive that was in use to
>> help meet GL5 specs would destroy anything brass in very short order.
> Excellent point about needing to double check the compatibility of any GL-5
> rated oil since GL-5 is not correct for these transmissions.  These older
> Audi/VW transmissions need an oil rated as acceptable for brass & copper
> corrosion stabilization,  which GL-5 does not give but GL-4 does.  In the
> past, AMSOIL had a 75w-90 GL-5 MT-1 rated oil that was acceptable for our
> transmissions.  Note that the MT-1 rating is what indicated that Amsoil's
> GL-5 oil was acceptable to use in the Audi/VW transmission.  The MT-1
> rating includes brass/copper corrosion testing that GL-5 does not.
> Amsoil has a new GL-4 rated 75w-90 transmission oil, so the stabilized GL-5
> MT-1 is no longer the choice for the VW/Audi transmission.  Use the new
> GL-4 rated 75w-90.  AMSOIL told me that the new oil is formulated on the
> thin side of the 75w-90 rating, which these transmissions like better.
> Note that this oil is listed under the transmission fluid section on the
> AMSOIL web site and not the gearcase oil section.  Contact me if you need
> help ordering as I buy oil from AMSOIL regularly.
> No, I am not a dealer.
> Eric
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