Transmission fluid - Redline MTL or GL-1

[Larry]

What's the preferred transmission fluid for a 5-speed X1/9? Redline MTL or GL-1?

Larry

 

[Steve Hoelscher]

Redline MTL.

NEVER GL1.

 

[Alain - The Red Scorpion]

Redline MTL.

NEVER GL1.

MTL 90 is synthetic oil. I use it in my 1995 Miata but I was told that it may not be suitable for order gearboxes like my 1980 X1/9 5-speed.

 

[GregS]

It's been the go to oil for X1/9's for a while now. In my 4 speed it improved the shifting from 2nd to 3rd, but strangely it balks now occasionally shifting from 3rd to 4th that it didn't do with the Castrol synthetic that I had in previously.

 

[Steve Hoelscher]

MTL 90 is synthetic oil. I use it in my 1995 Miata but I was told that it may not be suitable for order gearboxes like my 1980 X1/9 5-speed.

Redline MTL and MT90 are synthetic GL4 gear oil. As such, its fine for the X1/9 transaxle. I have been using it in both my competition and street X1/9 transmissions since the mid 1990s. I have tested most of the available options and nothing is better than Redline. Its the only gear oil I recommend for the units I build.

Never use any hypoid gear oil in an X1/9 transaxle.