75w140 gear oil OK for Subaru differentials?

[Eddie]

My Forester specs 80-90 front and 75-90 rear. I use 80-90 in both and have for 127,000+ miles. M1 80/90. I would not use a 140 gear oil in my Subaru.

 

[lewdwig]

Good to know as I changed the differentials in my daughter's Forester with 80W-90 (Valvoline DuraBlend) in both. The rear diff appeared to be factory fill (170k miles) as the drain plug was really hard to remove...thanks to the internet for the jack assist to the breaker bar trick.

 

[Bror Jace]

Captain Klink, I agree with Johnny and others ... don't use ATF to thin out a 75W-140 gear oil for use in trannies or diffs. It's bad practice to mix different app fluids with radically different add-packs. If you have mathematically calculated a desired cSt you want, mix 75W-90 and 75W-140 to reach that goal ... preferablly the same type and brand. That way you know the additive packages will be compliant and won't work against, and potentially degrade, each other.

Regardless, I look forward to your UOA ... please post in the gear oil section of this forum with a link back to this thread.

Eddie, as far as I know, there is no Mobil 1 80W-90 ... you must mean 80W-90 Mobil conventional gear oil, yes?