ATF and effect on Fuel Economy?

[Fat Charlie]

Originally Posted by ukiltmybrutha

I would ask more at bobistheoilguy but the conversation usually degenerates when mentioning that my question is FE based.

Tell them you're trying to shave a tenth off of your quarter time. They value that a lot more than something practical.

Originally Posted by JSH

In general: Yes. It is amazing how much of our fuel economy targets are hit with new fluids...

In practice: Run the fluid recommended by your manufacturer. It takes us more than a year and millions of miles on dynos, test tracks, and road testing to certify a new oil. There are a bunch of little tweaks that have to be made to use thinner oils. Changes to bearings, seals, oil passages, etc.

+1 on the results and the dangers. Even the "special" kids over at legacygt.com back a dozen years ago were warning about changing to synthetic on their little high compression turbos. They still couldn't bring themselves to admit that "better" wasn't actually better, but they did warn about leaking through seals and that you needed to check your level. But, you know, it was "better".

[Keito]

Be aware it may raise the stall speed on the converter.
I run John Deere Hy Guard hydraulic fluid in my race car auto transmission and have played with the viscosity to raise and lower stall speed.
Doesn't change it a ton but will most certainly change it.
Not sure the effect on MPG's, I only run a 1/4 mile at a time.

[matt36415]

Toyota WS fluid (Aurion- the Australian name for the V6 camry) uses it and the alternative I have moved to is Penrite Low Viscosity. What reasons would there be (other than fuel efficiency) for moving to thinner fluids?

[Ecky]

Originally Posted by matt36415

Toyota WS fluid (Aurion- the Australian name for the V6 camry) uses it and the alternative I have moved to is Penrite Low Viscosity. What reasons would there be (other than fuel efficiency) for moving to thinner fluids?

I can't speak for transmissions, but in engines thinner fluids tend to mean less wear queen fluids are cold.