I'm running Amsoil synthetic 75w90 now, feels and shifts great. My next fav would probably be a blend of regular Red Line synthetic with a quart of Red Line for syncro transmissions (the syncro stuff doesn't have the same friction modifiers as the regular stuff so your syncros can grab).

One time I tried the Suabru synthetic stuff they sell at dealerships, I was not pleased. It may have been to slick because it felt like my syncros weren't grabbing right.

 

whatever i decide to go with, i can run either dino 75w90 or synthetic 75w90 in both the trans, and the rear diff... correct?

 

You can.. I wouldn't, mainly because it gets left in there so long. Synthetic doesn't break down near as fast as dino oil.

 

so i should run a 75w90 synth. like... motul gear 300? That one seems to get the best reviews.. Ok to run in trans, and rear diff?
remember... 2004 wrx non sti

 

As long as your car is a manual and not an automatic, then yes. Although I'm not sure if it's designed for syncro mesh transmissions. If it has the friction modifiers it can cause the syncros to take a little longer to mesh up.

 

Subaru Extra-S

 

that^^

 

valvoline 75w90 dino

 

I use Valvoline regular 75W-90. So did my dealer last I checked. It meets SOA specs. It works.

 

I have been running this in my 2011 wrx for about 5 months now and it is crap, especially when it is cold. If is very hard to get my car in reverse and first gear until it warms up. I think I am going to try extra-s.

 

Subaru extra-s here as well.

 

my manual says use 75w90 for both gearbox and rear diff. It doesnt specify dino or synthetic. So i guess its ok to use either as long as its 75w90... right?

 

As long as it is GL5, which is specified in the manual. It's almost a given these days that a GL5 will be MT1, but in any case the manual specifies GL5 so that is what I use. The viscosity is given as a range depending on ambient temps; 75W-90 happens to be correct for my area.

 

Hey what about using red line 75w90 NS for gear and rear diff.
idk if it would work?
btw ive read that it works wonders on some trans and other are not pleased so im not sure if i should get it or not, maybe someone can help me out!

 

I won't bother with Redline. Regular geal oil instead. Valvoline regular gl5.

 

I dont have subaru extra - s in my country, Im from el salvador, all subarus here are imported from the US, so i dont have subaru authorized dealer, tried to ship it from the US and i need various permisions, so thats a NO,
sadly all i have is REDLINE and MOTUL300. also pennzoil 75w90 but GL4 so im kinda screwed.
So if u can help me with this i would really apreciate it!

 

I just did a tranny fluid change about 2 weekends ago. I went down to baxters auto since autozone did not have a single gear oil in stock lol. Got to the shelf at Baxters and saw the price tags on some of the qts and was blown away how ridiculously expensive it was , and the fact we need nearly 4 qt's to fill out tranny and front diff. Saw the Valvoline 75w90 for about half the price of the other brands. I remember reading not to put synthetic in because it is to slippery. Been driving on the Valvoline 75w90 and am impressed with how much smoother my down shifting is and how much more torque my tranny is consistently holding. I have an 02 wrx and temps outside is right around 70 degrees. Will wait to see how well it holds up during winter. I live in the northwest so we have mild summers and winters. I would suggest sticking with the cheaper stuff (Valvoline 75w90) , and getting the best bang for your buck.