5th Gen Subaru Impreza Forum banner

Differential Oil Change

27K views 3 replies 4 participants last post by  ferraiolo1  
#1 ·
In the 2018 Impreza manual, it says for severe driving conditions, the front and rear differential oil should be changed every 15k miles with Subaru Extra MT 75w-80 which is what it came from the factory with. You can use Subaru High Performance SAE 75w-90 but it will detract from driveability and fuel efficiency. If the car never sees severe driving conditions, it says to simply inspect it every 30k with no mention of replacing it all the way through 132k.

I'd like to replace the front and rear diff oil every 50k miles. So I went to buy the Subaru Extra MT 75w-80 and it only comes in a 5 gallon bucket that cost $400. I went to the dealership, they told me they just use the 75w-90 in all the cars and offered to sell it by the quart. WTF...
 
#3 · (Edited)
I don't know what manual you're looking at, but mine says 75W-90. Not to disregard Bruce's engineering background, but I'm willing to bet dollars to donuts that any API GL-5 classified 75W-90 would be fine. I used Valvoline SynPower 75W-90 (API GL-5 certified ) in my 5-speed Legacy and it loved it.

EDIT: I see the "*3" after the "Subaru Extra MT." So yes, this is 75W-80.
 

Attachments

#2 · (Edited)
My Subie dealer will always use Valvoline 75w90 unless SPECIFICALLY told to use the more-expensive Subaru Extra MT .

I have purchased Subaru Extra MT in less than 1 qt containers here is example ==>

https://i.ebayimg.com/images/g/YBEAAOSwsABaXt32/s-l225.jpg

The Subie manual xmission oil is SHARED with the front differential. This demands unique lubrication qualities. The xMission synchronizers need to have some 'grip' to reduce gear-clash.... at the same time, the hypoid-gear in the diff needs ExtremePressure (EP) additives.

I did a LOT of research before using Subaru Extra MT . It *really* does make a difference in shifting-feel, low-temperature operation, reduced gear-churn, and other xMission characteristics.

For the rear-differential, any quality 75w90 hypoid oil will suffice. (No need for the more-expensive Subaru Extra MT )

BTW: Virtually EVERY vehicle on the road falls into the "severe duty" usage category. Lets not forget that short-trips and cold-weather are considered "severe" because of the formation of water-condensation within the gearcases.