Best manual trans fluid for mpg

[dang10010]

Anyone try running thinner or synthetic gear oil? I believe the book said it could run on atf or gear oil.

[MrMazda92]

This won't make a noticeable difference for economy, but there are other potential reasons to switch. Personally, I think a high quality gear oil at the OEM recommended viscosity(75w90) will suit you just fine, especially if you're kind to your transmission when you drive.

[wagZE]

I run penzoil syncromesh, works great. Alot of people on mx6.com & probetalk use it too. Be weary of gear oils with sulfur in them- they eat away at copper synchros! Syncromesh is safe non corrosive for copper synchros in our transmissions.

[mitmaks]

I'm running Valvoline synthetic 75w90, there's no noticeable difference. Tranny shifts good and I'm happy

[MrMazda92]

My current gear oil in both cars is Redline(MT90?) IIRC. I've got some Amsoil synchromesh that'll be going in next time I do a change. The Redline has been pretty good to me, way smoother shifts than w/e came in my car after my tranny swap. I picked up the Amsoil for a steal, otherwise I wouldn't buy it so long before needing it.

[Mooneggs]

I've always used Royal Purple 75w 90 and my tranny has almost 200k on it and still going strong (including an MFactory LSD).

[MrMazda92]

I almost bought the royal purple you run Mark, but it was about 50% more than the Amsoil at the time! I couldn't help myself.

[Josh]

I am sold on Redline 75-90. I have run it in my cars for nearly 10 years with great results. does it improve mileage,... if it did/does its not that noticeable. It does reduce friction which results in smoother operation and less wear which are pluses.

Story:
Reason I run Redline and stick to it is years ago at a CorkSport meet I was being dumb and did a nice little burnout in my Turbo B6. Still using a F series trans at the time I cracked the case and blew the diff apart. Did not notice this until i pulled into the gas station in Portland (this is back when CS was in Portland OR) and all the fluid dumped out onto the ground. I drove the car with no fluid in it all the way to Marysville WA. 3+ hours home with no fluid. trans should have seized up but it didn't. the only issue I had was the clutch started slipping when I hit Olympia, it was a scary drive but I made it Just barely. So that's why I have stuck with Redline for as long as I have, had I not ran a synthetic fluid it probably would have seized. Reminded me of how my grand pappy used to sell Slick50, he had this little beater he would drive around from shop to shop with no oil pan on it to prove that the product worked.