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Re: Comparison Question

Got this from Redline on issue of comparison between synthetic gear
oils.  My owner's manual calls for SAE 80W or 80/W90 GL-4 trans/front
diff, and 90W GL-5 for rear axle/diff.  I would think the
straight-weight diff oil would be better than the multi for
straight-weight recommended application, but maybe I misunderstand. 
Offered for your reading pleasure.

'86 4kcsq
'90 100
'95 90cs

> >Dear Redline:
> >       I have three Audi's at home (actually one of them is outside in the
> >parking lot).  I am considering replacing the transmission/front
> >differential and rear differential in my '86 Audi 4000 cs quattro with
> >synthetic geal oil.  Some recommend Mobil 1, some Amsoil, and some
> >Redline.  How do these three synthetic gear lubes compare head to head?
> >Is your straight 90W better than the multi-grade since my owner's manual
> >discusses a 90W oil?  It is my understanding that additives give oil its
> >multi-weight flexibility.  Is such the case with your multi-weight gear
> >oil; and will you MT90 be better for a manufacturer recommended
> >straight-weight application?  Your response will be greatly appreciated.
> >       Thanks
> >       Mark W. Byrum, Jr.
> >       markbyrum@erols.com
> >
> >       113 South Saint Asaph Street
> >       Suite 200
> >       Alexandria, VA  22314
> >
> >       703.299.0704
Dave Granquist wrote:
 In your Audy transaxle, the recommendation is for a Synthetic 75W90
> that would be Red Line MT-90. In the rear differential, Audi calls for a
> 90W GL-5, I would recommend Red Line 75W90.
> Red Line Gear Oils use polyol ester base stocks, these are by nature a
> broad viscosity and offer increased protection, reduced temperature,
> improved cold lubrication and the highest film-strength available. The
> broad viscosity is prefered in the differential because it lubricates
> better at low tempertures, has less drag, uses less power and improves
> economy. Because the broad natural viscosity of Red Line lubes unstable
> thickeners are not required, so they won't sheer down. The Red Line will
> work better than a streight weight oil.
> Thank you for your interest in Red Line Oil.