Recommend Lube for Subaru WRX?

[Dave]

I bought a Subaru WRX and am thinking about switching the manual transmission and rear diff to syn oil soon.

Subaru recommends a 75W90 GL-5 oil for the transmission and rear end.

I've heard that Subaru manual transmissions can be sensitive to transmission fluid with the wrong one making it difficult to shift.

Based on the specs, I'm thinking of using either AMSOIL Series 2000 75W90 in the transmission and diff, or RedLine 75W90NS in the transmission and RedLine 75W90 in the diff, or a combination of the two.

Any feedback?

 

[Bror Jace]

Dave, are you interested in the best stuff available or are you merely experimenting?

Spector on this site is usually an Amsoil fan who's has used both and prefers the Red Line gear oils.

In synchromesh transmissions, I have used only the thinner Red Line MTL.

But testing the Amsoil after 10,000-20,000 miles and then switching to the Red Line for comparison testing would be interesting.

--- Bror Jace

 

[Dave]

I'd rather not experiment and stick with the stuff that's known to work well in this car. I don't want to mess with poor shifting.

Looks like RedLine 75W90NS will be going in the transmission and regular 75W90 in the rear diff unless someone talks me out of it!

 

[Dominic]

since the rear posi is a viscous posi you have nothing to worry about running a synthetic in the rear, since it will simply be gear lube only.

 

[Dave]

Yeah, I wasn't worried about the rear diff, mostly worried about the transmission, which I also understand shares fluid with the front (and center?) diff.