Thread: GL-4 75w-90 Synthetic question

Is 75w90 synthetic okay to refill my 5-speed in my 1993 SE-R?
Thanks

Supposedly yes, i do not like it though. I prefer Redline MTL or any other Redline trans fluids if you want something heavier. The Redline stuff feels much better and is a much smoother shift.

A GL-4 rated 75W-90 oil is exactly what the manual specifies. If you keep up with the maintenance, either dinosaur or synthetic will work fine for most people.

Probably well known in this forum, but GL-5 oil can be corrosive with brass sinchros. So better stick with GL-4 (also avoid oils that state "GL-4/GL-5" in their labels).

I use MT-90 in my trans.

I use Pennzoil Synchromesh, and love it. The transmission seems happy with it too, especially compared to the other trans fluids I've used. Only one I've used that was better was Silkolene.

While I didn't have any problems with synchromesh and it worked really well from what I can tell, besides developing 5th pop out that is but I wouldn't think that would have caused it, I would not use it again.

I just changed my transmission with the one I put together, and when I drained the trans that was in the car (while trans was still fairly warm) the synchromesh glugged out like water! I've never seen gear oil come out like that and I've worked on many cars, done many engine or trans swaps, used mt90 for the most part or valvoline 75/90 or 85/140 and none of them were so thin when they came out, trans warm or not..

I've got the Valvoline 85/140 now an so far so good, trans feels real good, no cold shifting issues, engine doesn't try to stall when I let the clutch out when its cold like some guys say, but then again its not winter yet lol.

I use AMSOIL 75W90 in mine. Like OP have said, make sure it is a GL4.

I've heard NOTHING but GOOD shit about AMSOIL, but I've never used it..

The first clutch job I ever did on a B13 I made the rookie mistake of not filling the trans back up. I drove the car for about 25 miles before I realized I had no trans fluid in it. I had did a fluid swap about 10k prior and had put AMSOIL 75W90 in. I filled the trans back up with fresh AMSOIL fluid and never had an issue with it for the next 2 years of me owning it. I believe the only reason I didnt grenade the trans is because of this AMSOIL. So needless to say I am a huge supporter of the stuff.