Been doing some gear oil comparisons for 6sp Audi

[jakecro]

Vehicle involved is 2000 Audi S4 6MT. I will be doing a trans oil change soon and have been doing some research.

Generally speaking, we can agree upon the following:
Redline is good.
Amsoil is good.


The preferred/recommended fill for the manual transmission is:
GL-4 spec, total fill ~2.45qt

Common recommendation for fluid from other owners:
1/3 Redline MTL (1.6pt/0.82qt)
2/3 Redline MT-90 (3.3pt/1.6qt)

Now, being the person that I am and wanting to look for other, equal or better, alternatives I began looking around and educating myself. The reason we mix the Redline products is to get a better cold shift while retaining smooth shifting when the fluid is up to operating temps. Below are the stats I found.

Redline MT-90
GL-4
75w90
15.6 cSt, Vis @ 100C
90 cSt, Vis @ 40C

Redline MTL
GL-4
75w80
10.6 cSt, Vis @ 100C
56.2 cSt, Vis @ 40C

I was really interested in using some Amsoil MTG, which is the same family as the Redline MT-90 but not related of course , due to the great reviews Amsoil sees as well as their reputation. The lack of personal experience from others on the forums had me a little anxious too. The specs for the MTG are hard to compare to the Redline since you are mixing two different viscosities.

Amsoil MTG
GL-4
75w90
14.7 cSt, Vis @ 100C
84.5 cSt, Vis @ 40C


Now this is where it gets interesting and may create room for some debate, I mean c'mon this IS QW. I ran some numbers to try to get the viscosity for the Redline mix since you are essentially using a percentage of each weight.

The combined viscosity:
13.8 cSt, Vis @ 100C
77.6 cSt, Vis @ 40C

I have to admit that it is darn close to vis rating of the Amsoil MTG.

Any thoughts or comments? Did I miss anything?

 

[Pablo]

Allow me to ask this. What is the viscosity of the factory oil?

 

[jakecro]

I don't have any information beyond the spec 75w90. I can't seem to find any sort of data sheet information.

 

[Audi Junkie]

FF is kinda heavy. I think overkill for stock car driven on NA roads. However, if the car is modded, maybe stay close to FF, which starts almost 15cSt, iirc.
The last car I researched was for the Astra, and it could take anything from ATF to full 75w-90. I went with Silkolene Pro SRG 75 Full Ester Race oil. It's a thin 75 that protects like a 90.

In your case, I'd blend Redline to meet your winter needs, which are kind of tough in Indiana. Try 1q MT-90 and the rest MTL.

 

[Johnny]

Is Red Line and Amsoil the only two that make a decent gear oil for this application?

 

[BobFout]

Originally Posted By: Johnny
Is Red Line and Amsoil the only two that make a decent gear oil for this application?


Valvoline makes a synthetic GL-4 of that visco I believe.

The Euro lubricators make good stuff too, LM, fuchs, pentosin etc.

 

[mechtech2]

jake - I see what you are getting at.
Sure, go try it.
A slight edge can go either way concerning shifting for this and other reasons. It depends on anyone's particular transmission, and how they shift.

 

[jakecro]

Originally Posted By: Johnny
Is Red Line and Amsoil the only two that make a decent gear oil for this application?


No, just the two I have been heavily considering. I have seen others highly recommend Motul 300 as well. Some have even suggested Lubro Moly 75w90.

 

[Gene K]

I wonder if factory fill is Castrol BOT 130 M or another WSD-M2C200-C fluid?

If so the Motorcraft XT-M5-QS (A Full GIV PAO Synthetic) Manual Transmission Lube affectionately known as "Honey" is the same as the Castrol.