Another Transmission Oil Thread

[Ronthebiker14]

I just wanted to make a post documenting my experience with different transmission oils in my 2013 FR-S since I haven’t found anyone that used the oil I ended up using.

My car suffers from the notorious 4th gear grind at or near redline. When I bought my car a few years ago it had Motul gear 300 in the transmission from the previous owner. I decided to change the fluid out for good measure and used Amsoil Manual Transmission oil 75W-90 and I noticed my car started to grind going into 4th when driving hard. I had not noticed that before and this is before I knew it was a common problem. After some research I decided to change the oil again for Motul and the problem improved to little to no grind.

Fast forward 2 years to a week ago it came time to change my transmission and diff oil again and decided to give Amsoil a go one more time on the off chance I maybe somehow used the wrong oil the first time. Whatcha know it did the same thing, 4th gear got noticeably worse when at or near redline.

Being the OCD person I am I decided to start experimenting (and piss away money) by trying a new gear oil I haven’t before; Redline MT-90. I saw 2 people report that this oil fixed their 4th gear grinding and I see it generally has a lot of good reviews especially for older Toyota trucks which I also own. So I swapped my fluid out again ANNND no change from Amsoil.

At this point I was getting a little irritated but I figured I’m already this deep into it might as well figure out what works best since there is only like 5 companies that make actual GL-4 transmission oil. I had read that Miata guys swear by the Ford Motorcraft Manual Transmission Fluid, (it should be called oil not fluid but whatever) but I couldn’t find any reports of people running it in our cars. So I decided to piss away more money today and spend $125 for 3 quarts of it at my local Ford dealership (it can be had for $80/3qts on Amazon but I was impatient).

I’m happy to report that this actually solved my issue and 4th gear feels slightly better than it did with fresh Motul and way better than Amsoil and Redline. I also think that 2nd gear crunch when it’s cold is a little bit better with the Ford stuff than the Motul. I will say the cold shifting of Amsoil felt the best out of all of them but I live in SoCal so 40 degrees is about as cold as it gets lol.

I also noticed that LiquiMoly makes a GL-4 transmission oil but I did not try it so that would be cool if someone has any experience with that stuff but it looks hard to come by. If you decide to use the Ford stuff like me make sure you get the one that says XT-M5-QS on the back of the bottle. The stuff isn’t clearly marked what it is in terms of weight but Motorcraft says XT-M5-QS is a GL-3/GL-4 SAW 75W-90 oil which is exactly what our cars call for.

TLDR: Amsoil might work good if you live where its cold and/or don’t drive your car hard, some people swear by Redline MT-90 but it didn’t work out in my case, Motul Gear 300 is probably the most widely accepted oil for our cars, but Ford Motorcraft XT-M5-QS is the best oil I’ve had in my car out of the 4 options and has the best 4th gear shifting out of any of the 4 oils I’ve tried.

Also as a side note to anyone changing their oils, all the crush washers for our cars can be found on Amazon for a fraction of the price compared to the dealership.

[JohnH]

good stuff thanks.

hey, if you feel like pissing away even more money, try some Pennzoil Synchroshift. People on here have had good results and its been used in other transmissions with good results too.