In my old subaru days, many folks at NASIOC swear by the Castrol Hypoy-C 80w90.

http://www.castrol.com/castrol/secti...tentId=7036192

Just wondering if this same oil can be used for our 8's rear diff which calls for GL-5 80w90 or 75w90. I know Redline 75w90 is most popular. I can get the Castrol at a local wal-mart very easily.

 

IDK man. I'm staying stock. That tends to hold up just good for DD conditions. If you use all that track stuff it tends to brake down faster over time that is if your on the track. Guess its only made for the track and running your car hard. So if your 8 is a DD why change?
Oh and you might have better luck posting in the racing section

 

Or searching on transmission, rear, diff.

There have been a few discussions over 4 yrs. that mentioned the use of rear end fluids.

 

yeah searching is ur best bet but i would jusst stick to a stock regualar gear lube 75w90

 

I don't see why you can't use the Hypoy-C as it meets all the specs.

 

yeah technically you would use it but if it's not tracked or driven hard on a daily basis what's the point? It's like buying a turbo and never getting into the boost!

 

So what do the Subie folks like for engine oil? We just got a Forester and I'll probably stick with Mobil1, but just wondering.

 

Hypoy-C is quite cheap compared to the Redline that is popular as diff oil for the rest of this forum. Unless you're saying there's no point in changing the diff oil at all, in which case I completely disagree. Oil degrades over time whether you're driving normally or racing.

 

I already read through the past threads on tranny/diff oil. It's same old same old... redline or royal purple. I like to see if anyone tried Castrol specifically this one since Subie folks seem to love it. Castrol also makes a synthetic 75w90 which is also sold at my local walmart. I like stuff that are easily available.

Mobil 1 is fine. I used that for my old JDM STi and Saabaru 92x Aero.

 

The problem with diff oil is that it's not as easy as tranny oil to tell a difference. Unless your diff fails, and this car seems to not have problems in that regard, it's hard to tell how well a diff oil is doing without an oil analysis, and I don't think many here have done used diff oil analysis