ATF and effect on Fuel Economy?
 

Does thinner ATF have a measurable effect on fuel economy in an automatic transmission?

Thanks.

The guys selling the thinner synthetic aft claim it gives up to 5% better fuel economy.

Thanks. I have a Volkswagen TDI. I have heard of folks running Dexron 6 in there. Anything thinner at operating temperatures?

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

Ain't that the truth.

I'd give it a shot. I expect you're not likely to damage anything so long as you're not feeling anything weird. Thinner fluid is more likely to mess up your shift quality before hurting anything, and in that case you just switch back.

Only straight 30 weight oil is acceptable per bob 50 wt in southern Texas.

Also we need more MTBE, leaded gas and no ethanol.


On a serious note TDI automatics (which are lifetime fills supposedly) are very temperamental, I would be careful experimenting

Don't know about the newer tranny, but the DSG has mandatory changes @60k

Appreciate the good humor. This is the notoriously bad 01m transmission that was supposed to be lifetime fluid equipped.

I have redline c+ laying around which is their improved variation of atf+4 used in the crappy Caravan transmission. Redline and a few transmission shops gave this fluid a thumbs up. It is a bit thicker at 100c though.

Dexron 6 looks like it might work out as well but it is probably thicker than the sheered off original fluid still in it at 170k.

I wonder if I should just put the c+ in there and focus on other fluids like oil.

You should see the guys over at bobistheoilguy when some guy went down to 10w30 from 5w40 oil and ultimately 0w5 oil lol! So much hate!

Guy gained like 10mpg or something!

In general: Yes. It is amazing how much of our fuel economy targets are hit with new fluids (Engine oil, Transmission oil, Differential oil) It is also maddening for me since I have to install storage and dispensing equipment in a bunch of assembly plants.

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.

My 2014 DSG is every 40K miles. $600 at the dealer

It would seem so. I switched the 01 Impala from one Amsoil ATF to another:

Amsoil O.E. Fuel Efficient ATF:

Kinematic Viscosity @ 100˚C, cSt (ASTM D445) -- 5.8
Kinematic Viscosity @ 40˚C, cSt (ASTM D445) --- 28.3

Amsoil Signature Series Fuel Efficient ATF:

Kinematic Viscosity @ 100˚C, cSt (ASTM D445) -- 6.3
Kinematic Viscosity @ 40˚C, cSt (ASTM D445) --- 30.8

The car was getting 1 MPG better, roughly speaking, on the O.E. ATF. I'm probably not changing it again until 2023, at least.

Data Sheets (Sources: )

O.E.: https://www.amsoil.com/lit/databulletins/g3190.pdf

Sig. Series: https://www.amsoil.com/lit/databulletins/g3110.pdf