I'm getting to convert the Miata to synthetic fluids.
I plan to use Red Line MTL in the transmission, but I'm not sure what to use in the Torsen. Searching the Spec Miata forum didn't clear up much.
On my last car, I THINK I used Red Line MT-90, but I've also heard about 75W-90. At $11 a quart, I want to get this right.
Disregard: I just discovered that MT-90 is 75W-90. Duh.
Just make sure you don't get the one with the friction modifier. That's for clutch based LSD's and you don't need it for a torsen LSD.
I used the Redline stuff and wasn't really impressed. This time around I'm putting the Diff back to simple mobil 1 75w90 and the trans is getting Pennziol syncromesh.
Some Mazda transmissions specify 90 weight - so MT90. Whether that is the same as 75-90 gear oil, I don't know. Its probably better to use the MT90 than the MTL in the tranny.
The "MT" stands for Manual Transmission, I think :) They have various additives to make the sychros work magically or something - Redline's website has some nice tech porn on it.
Go with the 75W90, that's the correct stuff for a Miata rear end. Doesn't matter if it's the NS (no slip) version or not, the friction modifiers won't make a difference in a Torsen.
