Transmission and diff fluid for 2020 BRZ
 

Been trying to get my hands on the Motul gear 300 75w90 fluid, but of course they’re still on back order everywhere. Going to start doing all the fluid changes myself. Can anybody recommend tranny/diff fluid for a 2020 BRZ that’s comparable to Motul? I was looking at Redline 75w90 & MT-90. Not entirely sure what the differences are. Any help is much appreciated

I initially wanted the motul for the ease of pouring but it was OOO so I went with red line. You can Google the difference from specification/additive perspective but it is my understanding MT90 is designed for transmissions.

No regrets. The complaint with the motul is that when cold, it shifts worse than stock because of its viscosity (which is also what probably makes it perform best in track conditions ). Red line shifts well in cold and warmed up.

What about the rear diff? What fluid goes in there?

I had shift issues in the heat and coming off the track with 300 75W90. Switched to Motul 75W140. No issues since. In the winter the first couple of miles you can not get to 1st unless you are at a complete stop but after that it is all good.

I'm currently using Redline MT-90 and Amsoil Severe Gear 75W90. I've always been a fan of Redline and it has worked well in all of my past cars.

Check out the CSG Maintenance packages for frs/brz/86 specific packages.

MT-90 is for transmission only, but 75W90NS can be used in both.

Pakelo DLS is great as well.

There's also AMSOIL 75W90 GL-4. They list 2 products under the same designation

Is the 75W90NS safe? I thought it was GL-5 but our transmissions use GL-4.

Yes :)

It's more shear resistant than a GL-4 rated fluid.

I thought there was something about GL-5 fluid that is bad for synchros though? Or, maybe it's something that doesn't universally apply to all GL-5 fluid?

It's likely not universal, but as a general rule, modern formulations wont have incompatible components.

E.g. old Motul 300V (think over a 2 decades ago) did not get along with E85. Modern 300V does.

Have tried Motul 300V and Redline MT-90, street and track...both are great when the car is warm, Redline is marginally better when the car is cold. I'm using MT-90 from here...

I use Motul's Gear 300 because everyone and their mother uses it - and I've used it in my WRX autocross car over the years. In the BRZ, it was a big upgrade over the stock 25k mile fluid when I initially did it, so I've stuck with it.

Redline would be my second choice and might even be technically better. I feel like many fluids are so darn close in performance, feel, and lubrication/protection.

Personally I haven't found any fluid that completely fixes the cold 1-2 shift issues these cars have.