Cost-no-object 75W-90 GL-5 for a differential?

[dparm]

Motul Gear 300, hands down. Long-proven severe duty record in race cars and unmatched viscometrics. Only other fluid that can come close to it on paper is Gulf's Competition gear oil, but that stuff is impossible to find here. Gear 300 is readily available.

Renewable Lube's 75w90 looks amazing too. Very high quality basestocks and RLI has a solid history of making quality engine oils -- the Audi RS4 FSI debacle comes to mind. It's rare to find a manufacturer take such an interest in formulating oils so specifically and to interact with its customers.

Caveat is that neither of these carry any manufacturer certs, so they fall into the category of "proven track record".

 

[dparm]

Originally Posted By: CT8
All regurgitated marketing claims aside can any one prove the differences between any of the major brands

Yes. Look at the certifications and tests they pass. That is the objective way to compare them beyond the obvious datasheet numbers.

I'm a bit disappointed to see that half of the posts in this thread were just people shilling for various brands and no technical reasons given. This should be a discussion about what separates good from great, not "I use X and it's good."

 

[tdi-rick]

Originally Posted By: dparm
Originally Posted By: CT8
All regurgitated marketing claims aside can any one prove the differences between any of the major brands


Yes. Look at the certifications and tests they pass. That is the objective way to compare them beyond the obvious datasheet numbers.

I'm a bit disappointed to see that half of the posts in this thread were just people shilling for various brands and no technical reasons given. This should be a discussion about what separates good from great, not "I use X and it's good."


True, but sometimes we can't pass on info due to professional in-confidence.

What I can say is that LE use a proprietory additive package, much like RLI, and it's extremely effective.

 

[dparm]

Originally Posted By: tdi-rick
True, but sometimes we can't pass on info due to professional in-confidence.

What I can say is that LE use a proprietory additive package, much like RLI, and it's extremely effective.

Understandable, but can we speak in generality?

 

[dparm]

One thing I'm noticing about the Delvac 75w90 is the extremely low VI of 140. Compared to something like Gear 300 (222), RLI (187), and Liqui-Moly (184), it makes me wonder if these others are using a lot of VIIs, or if this is just further evidence of vastly different chemistries. I was actually rather impressed to see the rather pedestrian GM Dexron LS 75w90 had a VI of 179.

However, Red Line's 75w90 also has a low VI of 155 which doesn't make sense given their usage of group V in many products.

What's the science behind VIIs (or not using VIIs) in gear lubes?