I'm about to try Redline 70W90 NS or whatever that number is...in Hawaii we have an actual REDLINE STORE!

 

I've was told by someone who builds race cars that the compounds they use in Redline are too thin, and no he wasn't sponsered by another company. I used Motul 300 gear oil w/ good success on my last car.

 

https://www.i-club.com/forums/drivetrain-67/check-out-swepco-lubricants-your-tranny-77545/

I love Redline products, but from what ppl who have used it told me I won't use their tranny fluid in my STi, nor did I with my WRX.

Many ppl just use the stock fluid.

If money is no condideration, use NEO, the oil that the Subaru WRC team uses.

 

NEO is just fine for your WRX or STi...it's just super expensive...

 

I've actually heard some bad things about NEO in the WRX 5MT from other boards (probably most notably www.wrxfanatics.com )

Redline gets my vote... especially the Shockproof HD. Use the 70W90NS (or whatever that is) if you want to stay within OEM specs...

 

A 1qt Synchromesh/balance 75w90 (I'm using Castrol Hypoy C) mix works well if you have any synchro issues (grinding shifting into first from a stop, mild downshift grinding) though, as with any aftermarket fluid, your transmission "warranty" could be voided if the dealer has the fluid analyzed. Your call.

Many synthetic gear oils are too slippery for the WRX synchros and can lead to grinding.

 

motul, put some in my car and its amazing

 

i just used redline 75-90 syn with the red line friction modifier and it works great! ive never known my tranny can be this nice! once i poured in the fluid and took it out for a test drive i noticed the shifts to be not as notchy and it just slid into gear! try this it works!

- i was going to try the syncro mesh but i hate penzoil there products are crap! thats just imo.

i wanted something that was proven in racing and i can trust. redline definatly has my vote now. i think the biggest thing that helped was the friction modifier. super smooth shifts, and i can shift into first above 20mph with no prob! ive had it in for a few hundred miles and all i can say is good things about it.

 

I have been using royal puple 75-90, works good. I also have used it in the diff

 

Standard reasonably-priced gear oil from local auto parts store, works just fine for the 5speed. I put synthetic in the motor but not in the transmission, too many stories on this message board of synthetic not working well with the stock gearbox.