2025 Forester Front Differential Fluid

[The Critic]

Subaru appears to allow "Extra MT" or a GL-5 75W90 for the front differential. Google is telling me that Extra MT is a 75W-80 GL-4 lube designed for MT's, which seems awfully light for a front differential.

Does anyone have a VOA of Extra MT?

 

[Glenda W.]

All I can come up with. Wondered the exact same thing when I did my Outback diffs.

 

[The Critic]

View attachment 268048
All I can come up with. Wondered the exact same thing when I did my Outback diffs.

Looks like Subaru only sells this in 5 gal drums. Closest matches are Redline MTL, Amsoil MTF and Motul's Motylgear 75W-80.

Motyl is the least expensive product but also likely to be the thickest when cold (highest 40C viscosity and lowest VI).

Ravenol is of a slightly lower viscosity than the 3 above.

Main issue is that the front differential is a differential. A lot of the MT specific lubes do not provide adequate protection for differentials. Does anyone know if Extra MT is a unicorn GL-5 75W80 product?

 

[D60]

Well, that feels very extra

Sorry, I had to.....

 

[Nuclear_42]

I’d just run Amsoil Severe gear or Valvoline 75w-90. I have 20k miles so far on severe gear on my 21 Outback no issues.

 

[Glenda W.]

I’d just run Amsoil Severe gear or Valvoline 75w-90. I have 20k miles so far on severe gear on my 21 Outback no issues.

Exactly what I did.

 

[The Critic]

I’d just run Amsoil Severe gear or Valvoline 75w-90. I have 20k miles so far on severe gear on my 21 Outback no issues.

I'm sure it's fine, but I would prefer the extra fuel economy. I cannot foresee wear being an issue in this application.

 

[Nuclear_42]

I'm sure it's fine, but I would prefer the extra fuel economy. I cannot foresee wear being an issue in this application.

You can buy it in 75w-85

https://www.amsoil.com/p/synthetic-75w85-gear-lube-svl/

 

[The Critic]

You can buy it in 75w-85

https://www.amsoil.com/p/synthetic-75w85-gear-lube-svl/

There is a significant viscosity difference between 75W80 and 75W85.

 

[twX]

Does anyone know if Extra MT is a unicorn GL-5 75W80 product?

It is a 75W-80 GL-5.

Another option for a GL-5 in that grade is Fuchs Titan Sintofluid 75W-80. It has better low temperature performance than the Motul.

 

[iCurious]

Is the Extra MT a requirement? If not, just use what it calls for GL-5, 75W-90.

 

[The Critic]

Is the Extra MT a requirement? If not, just use what it calls for GL-5, 75W-90.

It isn’t, but I also don’t see a reason to use a fluid that is nearly twice the viscosity.

 

[iCurious]

I think you are overthinking this because Subaru states 75W-90 to be used for both differentials.

But, hey, do what makes you happy.

 

[The Critic]

I think you are overthinking this because Subaru states 75W-90 to be used for both differentials.

Please read footnote #3 in my original post.

 

[oldhp]

2024 GMC Canyon 4X4. Factory rear gear goo is 75W80. That's too thin to me. GM doesn't state anything about going thicker when pulling trailer. I put Redline 75W90 in rear dif. Guess what happened to MPG??? Nothing, and it got down to 0°.
Also why does Subaru say 1.4qt in the front dif BUT only .8qt in the rear dif???? Seems backwards to me.

 

[GSCJR]

I've had 80w-90 in my 2012 Legacy diffs for at least 3 years now.

 

[iCurious]

Please read footnote #3 in my original post.

I did read the footnote. My statement still stands. But do what makes you happy.