Looking to change my trans and diff fluid soon, what your guy's go-to and why?
 

Looking to get my trans and diff fluid changed soon, what's your guy's pick and why? Narrowed it down to Redline, RP, and Motul............ or is it better to stick to OEM???

I use Motul as it seem to deal with heat better, which is nice during the hot summer and track days.

Motul, because it's been effective and seems to have completely removed my cold temperature shifting issue (below 0 degrees f) and also might have helped fix my 4th gear grind every time I'd shift into it at high RPM.

This could simply be due to the original fluid in the car being trash. I changed it a few months after I bought the car with 22,000 miles on it. I also really like that the cap has a built in funnel

Redline MT-90. Rated for GL-1, GL-3, GL4. The product description felt more appealing to me compared to other fluids I've used. Our aisin transmissions use GL-3. but GL-3 is obsolete so I use MT-90. Call me paranoid, but I personally do not like the GL4/5 products.

https://www.redlineoil.com/mt-90-75w90-gl-4-gear-oil

Got rid of stock for motul. Better shifting, and I've been happy with it.

The general consensus seems to be that Motul is the most popular option. I'll go with that one too come fluid change time.

I have Redline in mine. Zero issues.

Forgot to mention Amsoil. Excellent product also. And more readily available here in Canada.

Another one for Redline.

I've used Motul Motylgear (was better than stock), currently have Motul 300 (I think its about the same .. maybe better than the Motylgear).

Overall I'm happy with it. Occasionally 1st and 5th aren't too happy.



Another oil I've been debating is: https://products.liqui-moly.com/oils...ct-media-modal
I just tried LiquiMoly's engine oil additive CeraTec which has been pretty amazing.
I reached out to LiquiMoly and they recommended to use MoS2 isntead of Ceratec and their High Performance Gear Oil with the MoS2. So I'm debating that now.


This is LiquiMoly's email:
"thank you for sending us your request regarding Ceratec's use in manual transmissions.
Your manual transmission on your Scion is better of using our anti-friction additive named MoS2 Anti-Friction for Gears. This additive is specifically designed for use in gearboxes and differentials and will be the best choice for your 6 speed transmission. Lower internal friction will add protection to gears, bearings and synchros.
Also make sure to use a high quality gear oil in the transmission, like our High Performance Gear Oil GL4+ 75W90.

Please let me know if you have any questions.


Stefan Braun
Application Specialist"

Pennzoil synchromesh. 85k street miles and almost 2 full race seasons and not a single crunch or grind.

None of that fully synthetic stuff for me in the trans. Synchros like a little friction - their very job function specifically relies on it.

+1 for Amsoil in case you didn't eliminate it outright.

My thoughts:
https://www.ft86club.com/forums/showthread.php?t=127620

So far I've run the OEM fill, Toyota's recommended refill LV 75W, Amsoil, and Motul...all GL4 or lower (I think the Toyota LV 75W is GL3...). Of the 4, Amsoil performed noticeably worse when cold. Motul seems to edge out the OEM fill and Toyota LV 75W, but not by a whole lot. I might try Pennzoil Syncromesh next time.

I am thoroughly confused by which oil to use after reading almost every thread on this forum lol. I've had no issues with my oem fluids so far @ 30k miles and would like to stick with OEM fluids.

However, everyone on the forums states to not use GL5 rated fluid in the manual transmission, however, it seems like the only current oem option from Subaru is GL5 specification (SOA427V1700). So does this mean it is not safe to use oem fluid in our transmissions? Also, would this part number be just fine to use in the differential? (not sure if we need something specific for LSD). Thanks.

This is the OEM part I'm referring to: https://ftspeed.com/part/soa427v1700...-1qt-universal