1. Attachments are working again! Check out this thread for more details and to report any other bugs.

prius begs for better transaxle fluid

Discussion in 'Gen 2 Prius Technical Discussion' started by epoch_time, Apr 18, 2012.

  1. epoch_time

    epoch_time Active Member

    Joined:
    Dec 2, 2009
    234
    108
    0
    Location:
    las vegas
    Vehicle:
    2009 Prius
    Model:
    N/A
    I changed my genII transaxle fluid a week ago..
    I notice reduced mpg when accelerating from stop.
    But better mpg at crusing speed (above 45mph).

    I would say the new ws toyota atf is thicker than the old worn fluid.. my prius has 42k miles at atf change..

    I believe the new thicker fluid (at stop lights) is submersing the motor/gen rotors and making noticable slower acceleration....

    Once the motor rotors spin and sling off atf car rolls well and better than before....

    But car does not roll as well as it did with old fluid until car gets up to speed...

    I'm kind of thinking of filtering old atf and reinstalling...old thiiner fluid....

    I wish toyota would find thinner fluid thats labeled for prius transaxle only.....NOT FOR USE IN CONVENTIONAL AUTOMATIC TRANSMISSIONS !!!!

    Insidently Nissian hybrid transaxle looks exactly like prius gen III and requires nissan automatic transmission fluid... I can't rember the exact designation......Something like GS atf....

    While toyota ws atf seems to be the thinest atf I would like something thinner....

    I am also thinking of running atf at the low level limit (5mm below filler hole) anybody tried this ...
    or notice reduced fuel economy after atf change...???
     
  2. uart

    uart Senior Member

    Joined:
    Sep 7, 2009
    4,215
    1,200
    0
    Location:
    Australia
    Vehicle:
    2005 Prius
    I don't think anyone else here has noticed similar problems after changing their ATF. I know I certainly didn't. Two questions

    1. Are you sure you did the job properly?

    2. Are you sure you're not just imagining these differences?
     
  3. epoch_time

    epoch_time Active Member

    Joined:
    Dec 2, 2009
    234
    108
    0
    Location:
    las vegas
    Vehicle:
    2009 Prius
    Model:
    N/A
    Yes I did it properly and ...

    I am absolutely positive about the low speed economy loss....

    at 7 bars of hv battery charge and barely pressing accelerator from red light stops had amazing acceleration and great economy...

    I heated new atf bottles to 100 degrees farenhight just by rotating and shaking atf bottles while letting them sit in vegas sunlight... prius transaxle had cooled to 95 degrees at fill.... I hope temperatures were compatable....
     
  4. mmcdonal

    mmcdonal Active Member

    Joined:
    Feb 28, 2010
    666
    98
    16
    Location:
    Columbia MD
    Vehicle:
    2010 Prius
    Model:
    IV
    Sounds like a typical overfill issue to me (without know more about your process.)
     
  5. seilerts

    seilerts Battery Curmudgeon

    Joined:
    Mar 7, 2010
    3,326
    1,512
    38
    Location:
    Santa Fe, NM
    Vehicle:
    2005 Prius
  6. Patrick Wong

    Patrick Wong DIY Enthusiast

    Joined:
    Mar 8, 2008
    18,198
    6,461
    0
    Location:
    Green Valley, AZ
    Vehicle:
    2015 Prius
    Model:
    Two
    It sounds like you are more worried about a small mpg change and less worried about damaging the transaxle which would cost you a healthy four-figures if it fails and requires replacement. Your two suggestions of filtering used fluid and operating at the minimum fluid level both have the potential of flirting with transaxle damage.

    Yes, new ATF will be slightly more viscous compared to used fluid. However you've also correctly noted that new ATF WS is quite thin to begin with.

    I personally have not noticed mpg changes after changing ATF WS on my vehicles. If you find that mpg is good at cruising speed, then I doubt there is much wrong with your fluid level. However, it wouldn't hurt for you to ensure the transaxle ATF is not overfilled.
     
  7. epoch_time

    epoch_time Active Member

    Joined:
    Dec 2, 2009
    234
    108
    0
    Location:
    las vegas
    Vehicle:
    2009 Prius
    Model:
    N/A
    The day after I changed transaxle I did check level 2.5 oz fluid came out fill hole.

    ( I used a bubble level checking front to back and driver to passenger directions)

    I had drained 3.75 quarts and filled with 3.75 quarts...

    After letting 2.5 oz out there was a slight improvement but the economy was better before..

    I usually get 70 mpg (max 40mph) on my level test track now getting 60 mpg (still great).

    My dismay is the weaker acceleration from stop...

    My instant economy while accelerating to crusing speed is reduced by 10mpg....till crusing speed is obtained..

    Many prius genII owners have reported driverside sits lower...I think its because transaxle is heaver than ice and mounted off center toward driverside...

    This results is deeper fluid on mg2 rotor...

    (genIII mg2 rotor is much shorter in length....which has less contact with fluid).

    Fact prius genII rotors are half submerged in fluid at stop...

    Fact new fluid is thicker than old fluid.

    Fact automatic trans fluid for conventional autotrans is OK for prius but not BEST for prius...
     
  8. M8s

    M8s Retired and Lovin' It

    Joined:
    Sep 11, 2008
    614
    113
    33
    Location:
    Colorado and Arizona
    Vehicle:
    Other Hybrid
    Model:
    Limited
    I suppose the new oil is thicker than the oil that was removed. Greater viscosity would lead to greater drag, which would be more noticable at slower speeds.

    Motor and transmission oils are polymers, meaning they are long chain molecules. As oils age, the chains get broken due to shearing forces and other mechanical effects. So, the viscosity will decrease over time, in effect "thinning" the oil. I'm surprised it has so much of an effect as to be noticeable, though.
     
  9. seilerts

    seilerts Battery Curmudgeon

    Joined:
    Mar 7, 2010
    3,326
    1,512
    38
    Location:
    Santa Fe, NM
    Vehicle:
    2005 Prius
    You have controlled HV battery SoC during these experiments? SoC has the largest impact on MPG and acceleration.

    You have not let your 12V run down e.g. having the doors open and/or stereo on while doing your fluid change?

    I had a slight MPG increase when I did my first fluid change.
     
  10. edthefox5

    edthefox5 Senior Member

    Joined:
    Jul 25, 2007
    10,096
    4,795
    0
    Location:
    Clearwater, Florida
    Vehicle:
    2007 Prius
    Model:
    Two
    Why are you pre-heating the new ATF?

    And they do make a better fluid than WS. I have been running Redline D6 for almost 50,000 miles. And I felt the car was more quiet at speed.

    But I don't think putting in new WS should impact your mileage.
    Humor me and change the Inverter coolant. Its easy and cheap.
    You should see an instant small bump in mileage.

    Like Seilerts said check your 12 battery on the mfd as well. The ignition load number. Do it in the morning. Ever have to jump the car?
     
  11. Oldwolf

    Oldwolf Prius Enthusiast

    Joined:
    Feb 15, 2011
    816
    106
    0
    Location:
    NC
    Vehicle:
    2016 Prius v wagon
    Model:
    Four
    I didn't notice any difference when I changed my fluid with new Toyota WS.
     
  12. cnschult

    cnschult Active Member

    Joined:
    Jan 9, 2008
    772
    95
    0
    Location:
    Michigan
    Vehicle:
    2005 Prius
    Model:
    N/A
    OP should just put the old fluid back so he can enjoy the better FE, acceleration and $4000 bill from Toyota for a new Transaxle.
     
    1 person likes this.
  13. epoch_time

    epoch_time Active Member

    Joined:
    Dec 2, 2009
    234
    108
    0
    Location:
    las vegas
    Vehicle:
    2009 Prius
    Model:
    N/A

    Yes I have control soc.. I touch the brake as light as possible to achieve alll regen braking and little friction brake.. this will keep soc around 68% indefinately on my test track which consists of 4 x 1/2 mile legs to a total 2 mile square lap.

    I use a walmart cigarette digital volt meter perminatly in ligter jack and monitor 12 battery every minute... since owner ship....Believe me my 12v battery is great...
     
  14. epoch_time

    epoch_time Active Member

    Joined:
    Dec 2, 2009
    234
    108
    0
    Location:
    las vegas
    Vehicle:
    2009 Prius
    Model:
    N/A
    I preheated ws fluid in the sun in hopes that It wouldn't cause any unnessary expansion or contraction of mg windings.....which might crack its enamel winding insulation......This is my theory only..

    But I have seen posts where toyota says atf must be changed at a certain temperature......The prefeered temp. was not posted so don't ask me...
     
  15. edthefox5

    edthefox5 Senior Member

    Joined:
    Jul 25, 2007
    10,096
    4,795
    0
    Location:
    Clearwater, Florida
    Vehicle:
    2007 Prius
    Model:
    Two
    Temp related WS fluid change is in regards to the Toyota Tundra truck which uses the same magical fluid.
     
  16. edthefox5

    edthefox5 Senior Member

    Joined:
    Jul 25, 2007
    10,096
    4,795
    0
    Location:
    Clearwater, Florida
    Vehicle:
    2007 Prius
    Model:
    Two
    What happens to the windings during the normal course of the day when the car/trans could go from a 40F morning to its running temp of 135F + all day than it goes back to 30F while it sits all night in the winter? Now thats some contractions.
     
  17. cwerdna

    cwerdna Senior Member

    Joined:
    Sep 4, 2005
    12,544
    2,122
    1
    Location:
    SF Bay Area, CA
    Vehicle:
    2006 Prius
    You talking about the now defunct Altima Hybrid? http://www.nissanassist.com/documents/NPSB_09_059_FINAL.pdf lists what it requires.
     
  18. Politburo

    Politburo Active Member

    Joined:
    Feb 15, 2009
    971
    208
    0
    Vehicle:
    2009 Prius
    IIRC this will not accurately measure the 12v battery since the socket is only powered when the car is on. When the car is on, the 12v bus is continuously topped-up by the hybrid battery. This is how a low/bad 12v battery can cause FE decrease.
     
  19. seilerts

    seilerts Battery Curmudgeon

    Joined:
    Mar 7, 2010
    3,326
    1,512
    38
    Location:
    Santa Fe, NM
    Vehicle:
    2005 Prius
    A 12V monitor in the cig port will tell you about battery health in ACC. It is something that every Prius owner should have in the car, not necessarily plugged in all the time, but in case things get weird.

    This is starting to get interesting.

    Not too many people would go to this amount of trouble to conduct controlled experiments. If you are conducting a test loop under the same conditions every time (SoC, engine temperature, 12V full, tire pressures the same, no wind), then it is possible that you might notice an effect.

    Since you are being careful with all details, and are interested in getting the best fluid in there, how about running the same tests with Redline D6 and AMSOil ATL?
     
  20. edthefox5

    edthefox5 Senior Member

    Joined:
    Jul 25, 2007
    10,096
    4,795
    0
    Location:
    Clearwater, Florida
    Vehicle:
    2007 Prius
    Model:
    Two
    Amsoil has always been known to have great engine oil but really not known for tuner GL5 product. In fact in all the forums I have been on I see alot more Purple talk than Amsoil for GL5.

    I see alot of talk about Redline especially in Nissan tuner forums like FreshAlloy. I ran Redline in all my Nissans and was very pleased as it fixed alot of notchyness in the manual trans.
    In fact Redline fixed a 1-2 snicking in my Ranger truck that used ATF for its man 5 speed. The infamous M5OD trans.
    Redline is known better for its GL5 products. I tried Redline's engine oil once in the 20 weight and I could hear alot more valve train clatter which worried me so I dumped it and put Mobil 1 back in.
    Too slippery in that weight I think. Or maybe I was hearing things. That motor is pretty loud anyway.

    Redline engine oil is the strangest oil I have ever seen. It feels like liquid plastic between your fingers. Hard to describe but its pure base stock poly.
    I will someday try there 5-30 in my Prius though.