Differential fluid help needed

[tbolt1003]

I've spent the better part of this morning researching the proper fluid requirements for my differentials, and need help.

 

I'm going to be changing the fluid in both my front and rear diffs. I've found that a GL-5 with a viscocity of 75W-90 is the way to go. However, I'm seeing alot of people saying to use a full-synthetic, while others say any good non-synthetic will do. Some say the Subaru spec oil is the only acceptable route to go. Others say a fluid rated for limited slip diffs is needed. Alot of WRX and STi conversation, but little seen about the basic cars.

 

My car is a '95 Impreza L wagon with the 2.2, auto, 135,000 miles. Not looking to start one of those oil debates, just do I need anything special for my basic daily driver. Thanks!

[forester2002s]

I use WalMart's 80W90 in the rear-diff of my 2002 Forester MT.

When I change the oil, the old oil looks almost clear, with a very minor 'furring' on the drain-plug magnet.

I am happy with the oil. It seems to work just fine.

 

BTW, I don't have a Limited-slip differential.

[ocei77]

^+1. Std gear oil is fine. You don't want the limited slip type.

 

O.

[tbolt1003]

Thanks!! Helps to narrow down my selections on the shelves.

[porcupine73]

Right for the auto trans it doesn't matter as much. It does need to be GL-5. On that era even if you have a limited slip diff you don't need limited slip diff additive, because the Subaru limited slip (at least of that era) was a sealed viscous silicone type that the gear oil never even touches.

 

All the 'talk' you mentioned is likely for manual transmissions, those can be a little picky because if the friction characteristics aren't just right then the syncros don't get up to speed right and ends up with grinding in shifts.

 

When doing the rear - remove or at least loosen the fill plug first. There's been a few posts where people removed the drain plug first ... only to then find out they couldn't get the fill plug out.

Edited November 30, 2014 by porcupine73

[Aluxes]

Go with the Subaru Extra S. It is whats used in the STI. It works great!! Had the dealership change front and rear in my 97 imp. I noticed smoother rolling and a bump in mpg.

[tbolt1003]

Thank you for all the replies!!

[MilesFox]

For a front differential, assuming an automatic, 80w90 conventional or 75w90 blend or full syn., beying 90 grade oil. The GL-5 spec is for a pinion gear such as the font and rear diff. A GL-4 synchromesh is not appropriate for a subaru with manual trans considering the diff and a GL-5 rating. This is where the 'extra-s' fluid is relevant to a manual transmission of any type.

 

A 75w90 may give you better fuel economy and rolling resistance in cold weather. Front capacity is 1.3 and rear is .08. Two qt bottles will service both the front and rear for within 20 bucks. A gallon size container is not necessary.

 

For this 20 bucks i am using mobil1 75w90. walmart is cheapest

[Fairtax4me]

Plain 80w90 gear oil. I get the Walmart stuff for $12 a gallon.