Transmission Fluid

Which AWD? Prius AWD doesn’t have a conventional rear differential with fluid, as far as I know.<never mind…

I’m sceptical they would screw up on a spec like this.

 

That doesn't sound right to me, either....why would Toyota move away from the tried-and-true WS?? Even my rear differential in my 2021 AWD Prius just takes WS.
New models are sometimes slow for specific maintenance data to come out since they aren't needed right away.
Thankfully, you don't have to worry about it until you hit 5-years or 100,000 miles!

 

My rear AWD differential (2021) takes about 1.3 qts of WS....it's supposed to be changed every 25,000 miles so will be doing this service in a week or two when she hits 5,000 miles since her last oil change.

 

Seems to be correct.
Development of Transaxle Fluid for Electrification Vehicles
"The fuel economy in the Toyota Hybrid System (THS) was improved by 1.0% and more compared with the ATF because of the significant viscosity decrease in the developed fluid. This fluid will be widely used for HEVs, PHEVs, BEVs, and fuel cell electric vehicles (FCEVs) and can contribute to the realization of a carbon-neutral society."
Development of Transaxle Fluid for Electrification Vehicles: Design of Novel Additive Formulation

ATF has two main jobs; lubricate and act as a hydraulic fluid. The THS transaxle has no use for the hydraulic duties, but the ATF Toyota had on hand was lower viscosity than their fluid for manual transmissions. So that is what the Prius got. Over 20 years to develop something specific for their hybrids seems a bit long though.

The abstract doesn't cover it, but does this new fluid have a higher heat tolerance than the ATF?

 

The Crown is using the engine and hybrid system found in the Camry and Highlander and other models, which came out before the paper was published. Toyota will likely stick with the ATF in it.

Or you have a Platinum trim, which is a parallel hybrid with a true six speed transmission.

 

It is correct. It has reduced viscosity for higher fuel efficiency (E suffix), intended for MG-controlled transmissions as in Prius.

https://toyota-club.net/files/faq/03-03-29_e77-04_eng.htm

 

That is the e-transaxle fluid TE.

However, there is some hogwash in that Toyota paper, as there is no such thing as an oil-film-forming polymer. They are talking about the viscosity-modifier (VM)—also known as the viscosity-index improver (VII)—polymer, which does not contribute to the oil film in high-shear environments like a gearbox. Therefore, hopefully the increased antiwear-additive content will make up for the reduced oil-film thickness due to the reduced oil viscosity and we will not see increased transmission wear.

 

They are either being translated from Japanese by someone, or that is their own translation into English? They are likely Japanese first language thinking engineers, is my guess.
For me it is as simple as using what Toyota says to use, no second guessing them. So far, they haven’t failed me with wrong parts. Their testing is good. On my Prime, all I need to do is drive it and go by the manual. I tend to do more often oil changes, but not less. You can look at your own mpg and mpge and wonder “how did they do that?” I do anyway and it’s sort of a hallmark of Toyota, get more than expected. Not always, but often enough.

 

No, it is not a translation or foreign-language issue. It is a lack-of-knowledge issue. Few engineers know how the VIIs work as a function of the shear rate, and these certainly did not. A VII polymer would hardly contribute to the minimum oil-film thickness in a gearbox because of the very high shear rate. They certainly do contribute to the minimum oil-film thickness in journal bearings, but the shear rate there is much lower due to the different geometry.

Nevertheless, I agree with you that there is no reason to doubt that the new ATF will offer sufficient protection against transmission wear despite being much thinner.

 

Has anybody seen the Toyota Genuine Transaxle Fluid TE for sale anywhere?

I've been looking over the Owner's Manual for my wife's 2024 Corolla Hybrid and it calls for that in both the transmission and rear diff (it's the AWD) I guess Toyota is moving away from the WS, which is strange.

On Amsoil and Valvoline websites, there fluid said compatible with Toyota WS but doesn't mention the TE.

 

The WS is an automatic transmission fluid. It's engineered to work with a torque converter, which means compromises that hinder some properties more important to a hybrid or EV transaxle.

 

Hey there, does this mean Toyota TE and their WS ATF have alot in common? To the point where it’s okay to substitute one for another in stuff like the Rear Axel for the prius? Cheers!

 

From your initial post, in the thread you started:

also from that thread, a portion of the screen-grab from your owners manual, that I posted, the last paragraph in particular:



I’m just smart enough to defer to their advice in matters like this.

I’d “fold on that hand”, get enough of the specified fluid for 3 fluid changes, do them in succession, a few days apart, and move on. It’s likely overkill, but who knows.

I once poured about a cup of motor oil into our Honda’s automatic transmission before I woke up. The triple fluid change was the recommended remedy; I complied.

 

No, they are completely different, TE being far, far thinner than WS. TE is made by Eneos, whereas WS is made by Idemitsu. You can check their specs on their manufacturer websites.

 

The TE likely has more in common with a manual transmission or gear oil than an ATF. Actual property differences aside, I'd expect it to have a higher heat tolerance than any ATF. If a gen5 doesn't have the additional cooling the gen4 had for the ATF, the WS may degrade from higher heat.

 

Nope, the TE has a Group III base oil like the WS; so, both have the same heat tolerance.

And, nope, with KV100 = 3.3 cSt, it’s far thinner than any gear oil or manual-transmission oil out there.

ENEOS Toyota genuine EV/hybrid e-axle fluid TE

 

Made no claim about viscosity.

Additives are also a factor. ATFs have to account for the presence clutches and other parts in an automatic transmission that are of no concern in a hybrid transaxle. Toyota used WS in earlier hybrids cause it was likely lower viscosity than their off the shelf manual transmission fluid, and they didn't want to pay for an all new fluid until hybrids succeeded in the market.

 

I couldn’t verify that the WS is entirely Group III. It could be a Group II & Group III blend. So, the TE might have a tad bit higher heat tolerance than the WS.

They should all have plenty of antioxidant. Does the TE have more antioxidant the WS? Probably not, but it might.

The WS in my Gen 4 Prius Prime is good for “inspection” every six years; so, it has a fairly long life. I don’t know what the maintenance schedule is for the TE in Gen 5.

Again, the TE is the lowest-viscosity ATF in the market. There is the FE, which is thicker, and the WS is thicker than the FE. The reason for the viscosity lowering is to improve the fuel economy—just like they went down from SAE 5W-30 to 0W-20 to 0W-16 to 0W-8 with engine oil—nothing else.