To me the MT-90 while it is great for the normal gears and synchronizer operation may provide limited protection for the most expensive part, the ring and pinion set. To my surprise I am even seeing gear set failures in the automatics. I would want a god extreme pressure performance package and to me that is GL-5 or higher. For those that do a lot of high speed driving or have bigger engines attention to viscosity is also important. Many synthetic lubricants tend o run at lower actual viscosities and that is part of how they get the increased efficiencies. Unfortunately like the Vanagon engines there are conditions where the oil becomes thermally challenged where the loss of viscosity becomes a problem along with the overheated parts  which can cause failures not related to just the lubrication. I have been filling some boxes with 75w-110 (Amsoil) and also 75w-140 for the extreme abusers. 

Dennis

-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of JRodgers
Sent: Saturday, June 21, 2014 8:17 AM
To: vanagon@GERRY.VANAGON.COM
Subject: Re: AA Transaxle: Happy! Relevant Info, Long.

Neil, why not? Been using Redline MT 90 for years - and Ol' Red is due a tranny oil change next month, and I was going to use the same Redline.
So - what's the thinking?

Thanks,

John

On 6/20/2014 1:48 PM, Neil N wrote:
> Not sure I'll run Redline
> MT again though.