ATF change and fuel economy

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by NewHybridOwner, Nov 6, 2020.

  1. NewHybridOwner

    NewHybridOwner Active Member

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    I came across Prof. John Kelly's YouTube video about the history of Toyota's various ATF specifications, and toward the end, in dealing with the WS ATF, he suggests that over the 17 years since it was first developed the formula had undergone some revisions for various reasons, perhaps including for greater fuel economy.



    This has got me wondering whether anyone has seen improvements (or otherwise) in their gas mileage after changing their ATF.
     
  2. Mdv55

    Mdv55 Member

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    I've been running Amsoil ATF, which is slightly thicker then WS, for the past 50K. No change in fuel economy and I still average 50mpg overall.

    I doubt less then 3 quarts of ATF is going to have any measurable effect on fuel economy. If you talking large amounts like in a Tundra that holds 4x the amount of ATF then I'm sure the difference starts to add up.
     
  3. edthefox5

    edthefox5 Senior Member

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    Prof kelly is referencing the 2 types of trans fluid. The one in the picture is the older type T and the newer type WS is a thinner viscosity fluid essentially a Dexron 6 so they gained a tiny bit of mileage with the newer thinner fluid just like they did with motor oil. Your car uses the WS fluid.

    And Motor oil was always 5-30 or 10-30 now most modern cars specify a thinner 20 weight oil for mileage gain. Very slight mileage gain.

    So I would not expect to see any mileage gains just changing your trans fluid it already has the thinner WS fluid.
    I have changed my 07's 3 times saw no mileage gain and I use a much better product & fully synthetic than WS.

    If you want to see mileage gains doing maintenance things change the Inverter fluid. You will see mileage gain there.
     
  4. Mdv55

    Mdv55 Member

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    Oh?
     
  5. jerrymildred

    jerrymildred Senior Member

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    Did Todd over at Tampa Hybrids give you that tip, Ed? He said something similar to me once. I wish I'd asked him more about that. I'm mystified, but the guy really knows his stuff.
     
  6. edthefox5

    edthefox5 Senior Member

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    Hey Jerry no I saw this myself after every Inverter coolant change. I saw a good mpg improvement. The biggest bump was the first change after its first 5000 miles then lower gains on the 2nd & 3rd. But that first 5000 mile from bought new was noticeable.
    And its circulation behavior changed drastically. When stock at 5000 miles it was somewhat tepid you could see it roll around a little but after that change it now looks like its at a fast boil. Really moving in there.
    been like that for years now. Always 90-100 degrees cooler than the engine temp.

    The cooler the inverter the more efficient the system is.

    This is why they separated rads on the G3 and on. No heat soak from the ICE coolant and more powerful mgs and Inverter to cool.

    I use a bottle of Redline Water Wetter in the Inverter reservoir also. Its a great anti foam agent it eliminates bubbles and vapor barrier. I see no foam or bubbles in the aggressive movement of the coolant.
    Its in my inverter tank and all the radiators in all my cars. Works great.
     
    #6 edthefox5, Nov 7, 2020
    Last edited: Nov 7, 2020
    jerrymildred and audiodave like this.
  7. Majafamily

    Majafamily Member

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    I changed all my fluids at 65k and noticed no change in mpg. I'm now at roughly 66.5k miles.
     
  8. NewHybridOwner

    NewHybridOwner Active Member

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    No. Prof. Kelly was doubting that even the WS ATF has remained unchanged in the almost two decades since it was introduced -- that even without a name change the formula may have changed. Only a theory, of course, and I was wondering whether anyone had noticed a change in mpg since changing the ATF.
     
  9. edthefox5

    edthefox5 Senior Member

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    Ok. I know its still a non synthetic d6 viscosity fluid with a big calcium package based on UOA's I have done. calcium mitigates acid which is why it touts long life never have to touch it but calcium is also a wear agent so there's a dance there. Nothing special there other than its viscosity which most are moving to a D6.

    For me and my G2 it is super easy and inexpensive to change. I use a much better product then WS anyway.
    A G3 is a little harder to change but not much. Easily done in your driveway hard part is taking off the cover.

    But I have seen a few photos of G3 fluid pulled and they looked 100% worse than any G2 fluid I have seen. Alot of initial wear there which makes sense alot more power going on in the transmission there than a G2.

    Listen you are all focused on mpg's. 100,000 miles down the road all your gas savings will go out the window if one major system fails on the car and your at the dealer's mercy at $150 an hour.
    The Prius is going to get very good mileage no matter what you do its really all about extending the life of the car and keeping it off the repair rack. The best way to do that is maintenance.

    On a G3 that's EGR. But it doesn't hurt to change the trans fluid and the inverter fluid.
     
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