Suitable substitutes for the Toyota ATF-WS transmission or transaxle fluid?

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by Rocketboy235, Aug 27, 2017.

  1. Mdv55

    Mdv55 Active Member

    Joined:
    Dec 25, 2018
    204
    145
    0
    Location:
    Boston
    Vehicle:
    2011 Prius
    Model:
    Three
    I don't put much stock in the hybrid components degrading fluid electrically or that special fluid is needed to protect them. Yes, Toyota took care in segregating the windings from the lubricant. People are assuming that WS ATF has some magical component that protects this resin rather then taking the viewpoint that the goal was to keep ANY lubricant out in general. Since the primary difference between conventional transmissions and hybrids is electricity people are running with the theory that the fluid has to have some special properties that help these components. Nowhere is there evidence this is actually true. To the contrary, there are people running Amsoil, Redline and more predominately Valvoline MaxLife without issue. As has been stated, failures in a Gen 3 transaxle are at the bottom of the list of things that sideline these cars.

    If you disregard all the hybrid components, at the end of the day, there is still a commonality with every other FWD transaxle out there. That is a differential that is going to squeeze and shear the hell out of fluid as it transfers power. Conventionally, a 30K change interval used to be the norm for changing differential fluid. Prior to manufacturers covering maintanence BMW used to recommend transmission and differential fluid changes at 1200 miles to remove break in debris.

    Bottom line is that the fluid goes through heat cycles in everyday use and most likely tracks fairly close with the temps MG1 and 2 are running at. This effects the fluid chemically over time. Additionally, the fluid is compressed as it pumped through the transaxle and squeezed and sheared as it helps cool and lubricate all the gears in there. All these are what is going to degrade the fluid over time.

    Here is what the inside of a Gen 3 transaxle, transmission, HSD, power split device or whatever people want to call it looks like...

    priustransaxle.jpg
     
    jzchen likes this.
  2. jzchen

    jzchen Senior Member

    Joined:
    Apr 9, 2012
    2,544
    774
    0
    Location:
    Arcadia, CA
    Vehicle:
    2012 Prius v wagon
    Model:
    Five
    From the technical article referenced the resin, (my apologies didn't catch the spelling difference my son uses rosin on his cello but this one is "resin"), was improved to resist oil (I'm assuming the WS in this case), so that the separation was no longer necessary...

    I noticed there is no language like WS was chosen due to electrical resistance nor resin compatibility...

    REVVL V+ 5G ?
     
    #422 jzchen, Oct 17, 2021
    Last edited: Oct 17, 2021
  3. ChapmanF

    ChapmanF Senior Member

    Joined:
    Mar 30, 2008
    14,569
    10,255
    0
    Location:
    Indiana, USA
    Vehicle:
    2010 Prius
    Model:
    IV
    The only way we could agree to that would be if a laboratory test showed the WS had recognizable components of the resin dissolved in it. The mere fact that we know they changed a previous resin formula, to be more resistant to the lubricant they were testing with, is not evidence that the later resin formula dissolves in the same lubricant. That would be strange indeed, if that was just what they reformulated the resin to avoid.

    They don't keep the lubricant out. They did in Gen 0, but eliminated that seal friction for Gen 1. Instead, they reformulated the insulating resin to be more resistant to whatever lubricant they were testing with, so they would not need to keep the lubricant out.

    You are certainly emphasizing the common aspects between the Prius transaxle and other FWD transaxles. We do know those aspects are common.

    We also know that the hybrid aspects hidden behind your "if you disregard" are aspects that are not common between the two types. The other FWD transaxles do not have HV electrical windings in them. That's not an assumption, it is a difference we know about.

    We know that compatibility of the electrical insulation, with whatever lubricant they used in testing, was something they had to engineer for, and involved at least one reformulation of a resin. That isn't an assumption, it's something we know from what Toyota published about the transaxle's development.

    We don't have a statement anywhere (that I've seen) saying WS is for sure the only lubricant compatible with the resin they developed. We could assume that all lubricants are equally compatible with it, even ones not tested for that property, which isn't part of conventional transaxle lubricant testing. That is what you're assuming, and it might turn out to be a perfectly ok assumption. It's just worthwhile to keep clear about what is and isn't being assumed.
     
    jzchen and Ed Beaty like this.
  4. Mdv55

    Mdv55 Active Member

    Joined:
    Dec 25, 2018
    204
    145
    0
    Location:
    Boston
    Vehicle:
    2011 Prius
    Model:
    Three
    Out of contact with the windings vs out the case would have been a better way to put it.
    I was trying to get at why the fluid would degrade outside of the vehicle being a hybrid.

    Yes, it's been discussed that the resin was a consideration. Personally I believe the resin was what was reformulated to fit the application, not that WS was created so it could be used in the Prius. Others believe that the owners manual admonition that only WS be used is proof that the fluid is needed in the hybrid and those of us who use other options are risking serious damage. None of us have direct evidence to make this more then opinion.

    What I'd also note is that there is no evidence that WS, err world standard, ATF was specifically engineered for the Prius. I would find that quite surprising actually. The spec was released in 2002 and showed up in numerous applications for the 2004 MY. I think it's more coincidence that was the first year for Gen2 rather a smoking gun that WS was developed for the Prius and it just happens that Toyota used it in their most popular transmissions and transitioned all the conventional automatics over to it.

    As has been previously noted, other manufacturers released similar fluid specs, Dex VI, Mercon LV and ULV, Kia/Hyundai SPIV etc... A more stable, longer lasting, low viscosity fluid was where the industry shifted too
     
  5. ChapmanF

    ChapmanF Senior Member

    Joined:
    Mar 30, 2008
    14,569
    10,255
    0
    Location:
    Indiana, USA
    Vehicle:
    2010 Prius
    Model:
    IV
    Still, if it isn't kept out of the area, as it hasn't been since Gen 0, it's only the resin on the windings that keeps the lubricant "out of contact with the windings", if that's the way you want to say it. Hence the reformulation of the resin.

    It's clear that WS is used in many Toyota vehicles and not something specific to the Prius. For that matter, the resin was reformulated between Gen 0 and Gen 1, which used T-IV, not WS. So addressing whether "WS was created so it could be used in the Prius" seems to be a straw man, a response to something that isn't proposed ...

    ... and so many words addressed to a straw man may only muddy the water.

    The owners' manual admonition is there. If someone, say Mendel, points it out, that may or may not tell us a lot about what Mendel personally believes. He might, for example, believe that it's worthwhile mentioning what the owners' manual says, in a PriusChat thread where people will come and read about the topic.

    The "risking serious damage" bit isn't coming from Mendel, it's right there in the admonition that's right there in the manual. Again, nothing much really hinges on whether he personally thinks that passage "is proof that the fluid is needed in the hybrid", or maybe just that readers of the thread deserve to see it themselves.

    Pretty much everything is opinion, but opinions aren't atoms; they can be examined to see what assumptions were needed to arrive at them.

    Remembering the things we do know:

    • a Prius transaxle has aspects that are common to conventional transaxles, plus at least one aspect that's distinct
    • one distinct aspect required an engineering effort to formulate a resin for resistance to (at least some kinds of) oil
    • polymer resins are often messy formulas of hydrocarbons and other stuff, and so are oils, and interactions between them can be complicated and require testing individual combinations

    it is possible to assume that other oils, not specifically tested against a requirement conventional trannies don't have, will still perform equally well on that requirement, or well enough that it won't matter. You're free to make that assumption; you don't need anybody else's permission, and it could turn out ok.

    By the same token, if there are others choosing not to make that assumption, that doesn't mean they have to be assuming the opposite is true or proven. They might just prefer to avoid the assumption.
     
    #425 ChapmanF, Oct 17, 2021
    Last edited: Oct 17, 2021
    Mendel Leisk and Ed Beaty like this.
  6. Mdv55

    Mdv55 Active Member

    Joined:
    Dec 25, 2018
    204
    145
    0
    Location:
    Boston
    Vehicle:
    2011 Prius
    Model:
    Three
    Interesting. I didn't catch that the memo was about Gen 0 and Gen 1 and thought it was about Gen 1 and 2. No clue Gen 0 was a thing until you mentioned it. That little tidbit and Gen 1 using T-IV just reinforces my opinion about the fluid not needing to be anything "special" to protect the resin and that Toyota's owner manual admonishment is nothing more then typical legalese to potentially limit warranty liability if needed.
     
  7. ChapmanF

    ChapmanF Senior Member

    Joined:
    Mar 30, 2008
    14,569
    10,255
    0
    Location:
    Indiana, USA
    Vehicle:
    2010 Prius
    Model:
    IV
    Again, you are free to assume that fluids Toyota was not testing with, while specifically reformulating a resin to be resistant to some fluids, will perform as well on that measure as what they were testing with. I agree we have no smoking-gun evidence showing that assumption is wrong.

    Others may, nevertheless, prefer not to make it.
     
    Ed Beaty likes this.
  8. jzchen

    jzchen Senior Member

    Joined:
    Apr 9, 2012
    2,544
    774
    0
    Location:
    Arcadia, CA
    Vehicle:
    2012 Prius v wagon
    Model:
    Five
    I definitely skipped some parts and glazed over on some parts of the article. Definitely did not catch which generations they were referencing. Thanks for clarifying!....

    REVVL V+ 5G ?
     
Loading...