Don't do it.  I did this same thing, and the Mobil One is much thinner than
the stock tranny fluid that it blew out all my seals, and ruined a  4-speed
that sounds like it was in similar shape to yours.

Replace the seals to new first if you want to proceed.......

Adam Puzerewski
81 westy
----- Original Message -----
From: "SpaceKommander" <jboldway@COTTAGESOFT.COM>
To: <vanagon@GERRY.VANAGON.COM>
Sent: Sunday, June 11, 2000 1:38 AM
Subject: [VANAGON] 85 westfalia tranny lube question

> Question - does anybody have any experience using Mobil 1 Gearcase lube
> (75-90 synthetic)? I've got a '85 westfalia and am thikning of replacing
> the tranny/differential with Mobil 1. Shifting is getting laborious (yes,
> is adjusted correctly) and am interested in getting as long out of this as
> I can . . . .