ATF fluid changes ARE Required.

I'll just throw this out there.

I've seen all the oil analysis info, and read a whole bunch of anecdotal information, but the fact of the matter is this:

With around 30% of the cars on the road in Japan being hybrids, and 50% of the cars on the road being Toyota's, NO ONE changes the HSD transaxle oil... Ever... Lots and lots, and lots of cars with over 300,000km on the clock, and transaxle failure in gen3 and on cars is rare. When it does happen, it's usually an electrical issue.

If you want to change the oil because it makes you feel better, more power to you. But the hysteria I've seen on this site is ridiculous.

 

With 180,000 on the factory fill, that's believable. WS is specifically formulated without metals in the dispersants (which is why it turns a "dirty" color quickly). With high mileage, and higher metal content in the oil, leakage current is sure to increase, making the system less efficient.

 

I wonder how electrical issues are related to the oil higher metal content.

 

So far as I know, Toyota is not using their windshield wiper fluid to cool parts running at 550 VAC. If another vendor certifies their ATF to be as electrically insulating as ATF WS, it would begin to consider alternatives. So far, that has not happened.

 

Toyota tells me to use Toyota ATF-WS, and cautions that using anything else could damage the transaxle. I'm ok with that. And when I trade-in the car I'm not handing a potential headache to the next owner.

 

Yep, remember "I'm outa here"?

 

The important aspect is that the fluid was changed.
$40.00 plus ( 2 jack stands that I had ).
When will my next fluid change be 50k from now or less?
I want to keep this car going for the long haul.
Yes I brand shop and if this was a standard transmission I would not be too concerned.
Buy brand name fluid like valvoline whatever at 6-7 bucks a quart.
Prius only requiring 3.75 quarts who cares? 4 quarts saved $3.00 each?
Some car owners plan to keep their cars for 100k then trade up.
Some buy at 180k like me and want to see how far it can go.
Somewhere in this thread is a discussion about viscosity.
I am now temporarily a brainwashed consumer believing that
I can only use toyota ws fluid.
Here is the big question parts of a penny per mile?
4 quarts of trans fluid $5.00 per quart from walleye mart = $20.00
4 quarts of trans fluid $9.99 per quart from toyota = $39.96
$19.96 saved
*If my next brainwashed not in the toyota manual fluid change was 50 thousand miles what is the price difference per mile?


The most incredible thing everyone should be talking about is how well designed this car is.
180k on a transmission no fluid change is simply exceptional compared to a standard auto transmission.

 

The more conductive the fluid becomes, the higher the current leakage. This translates to lost efficiency.

 

Depends on what's "acceptable." Who specifies this? I can tell you that a typical automatic is much more sensitive to debris, as it causes sticky solenoids, and spool valves. But Toyota says these transmissions are also a "lifetime" fill... Typical cars in Japan probably run to 200,000-250,000 km at the outside. If a car will run to 300,000+km on the factory fill, and doesn't break due to not changing the oil, is that "acceptable?" I'd say yes to that.

WS goes dark quickly due to the dispersants they use. Metal-based dispersants keep the oil "cleaner" looking, longer, and are the standard for most transmissions that I know of. Oil for hybrid transaxles purposely don't use metal-based dispersants.

Plenty of SAE technical papers that address hybrid transaxle oil, and the efficiency gains and losses using different blends that increase/decrease conductivity of the oil. Once again, metal-based dispersants showed high enough losses to keep them from using them, even though they're better. I don't find it a huge leap to assume that increased metal content in the oil, from wear, would add to this. In fact, I'm pretty sure one of the tests I read addressed it, They compared the conductivity of the oil with different dispersants, over time, and all of the oil had decreased insulation, but the non-metallic based dispersant oils fair much better. 'Leakage current" is a very real thing. How about electric motor bathed in a fluid...?

A generic SAE paper about lubricants in hybrid transaxles, and the effects of conductivity of the fluid can be found here: Lubricants for (Hybrid) Electric Transmissions

Keeping in mind that I'm not saying not to change the oil. I do it at 100,000km intervals, and recommend to customers to do the same. But that advice is based on no more than a "feeling." I have no evidence to show that not changing the transaxle oil over the course of 300,000+km is going to kill it. Why grind the gears and bearings with dirty lube if you don't have to? Why change the oil if you don't have to? I see them all the time, and my oldest son works for Toyota as a tech in Yokohama. They service taxi fleets with way over 300,000km on them, they don't change the transaxle oil, and they don't see lube-driven failures. So why change the oil if you don't have to? Being honest, if one of my customers is going to keep the car for 10 years, and drive it under 300,000km, evidence shows that changing the oil is wasting their money. Also keep in mind that we don't average the same speeds as the US does. People drive fast on the expressways, but the average speed a hybrid sees over it's life in Japan is much lower than the US. You are bound to have more wear.

I've never even heard of this.

WS is not just another ATF. It is made for use in hybrid transaxles. I've seen plenty of Honda transmissions destroyed from people not using OEM specified fluid, but that's a clutch and valve body issue. The Toyota hybrid transaxle only needs lube for the gears and bearings, so you probably won't hurt anything using a fluid that's not OEM certified...but can you be sure? I don't know, and neither does anyone else outside of Toyota. I do know that hybrid transaxle oils are engineered to be less conductive. I will also say that it's strange to want to change the oil based on no evidence of dirty fluid-caused failure (trying to keep the transmission in good shape), but also want to put something other than what the manufacturer says to use, without any knowledge of what they want, or why they want it (possibly doing horrible damage to the transmission). Is there something in WS that helps carry away heat? It's a coolant, after all. What about long term degradation of the motor winding insulation? Is there something in WS to protect against this that's not present in high-dollar, non certified ("meets or exceeds" is not certified) lubes? I don't know, but neither does anyone else. Interesting gamble, though. What if you ruin the transaxle using a non-certified oil? Will they honor the warranty? Plenty of manufacturers now running oil samples on destroyed engines, and not warrantying them. Toyota now has a service bulletin telling techs how to identify a modified battery pack, and won't warranty them if they've been touched. We use OEM oil at mostly OEM intervals, and have no issues. See way more issues from people deviating from what the OEM says to do...like using cheap 5W-30 in a Pruis. Going back to Toyota 0W-20 for a few changes has fixed plenty of oil burners.

Once again, not saying not to change the oil. It might be good insurance. But without a failure pattern linked to not servicing the transaxle, they hysteria is completely unfounded.

 

Stator insulation is supposed to work properly. Can you explain?

 

I'm a fan of the 60k mile transaxle oil change. And, agree wholeheartedly. There could be all kinds of differences between WS and other "compatible" transmission fluids. Odds are probably good that Toyota contracts some major manufactuer (such as Castrol/Mobil/etc...) to manufacture the oil. It could be that they do so under a strict confidentiality and commercial agreement that their formulation not be manufactured for any other purpose/brand.

Who knows? All I know is that if I'm going to go through the extra effort to crawl around on my garage floor every 60k miles and go through the hassle of changing that stuff - I want to have it be the most likely best fluid for the application. And absent information from a Toyota Engineer charged with the responsibility of lubrication formulation - the most likely best fluid is Toyota's WS...

 

WS was not "designed" for Toyota hybrid transaxles...it is also used in them. Additionally...like any "gearbox" or motor lubricant an early fluid change does rid break-in deris and assembly contaminants and regular fluid exchanges extend the service life of said components. That fact that some components are better made than others only reflects on the design of that component, not the need (or lack of) for service. The service life of a fluid is not determined by when a component fails...or is out of warranty.

 

There's been a few mentions of 60,000 miles as a good interval. I'd qualify that to stress: a much earlier first change seems beneficial, judging from the appearance of the fluid I drained at the one year mark; it was quite dark. Left it a couple of years for the next drain, and that stuff looked almost new.

I won't mention the km's involved, I might be put away.

 

With hindsight I should have done my first at 10,000 miles...and will on my 2015. 30,000 miles is my regular interval...but what do I know? I'm just some lowly Mechanic.

 

Hi Frodoz, I don't think I ever said it was designed for them. I just said that it is most likely the best fluid for them... This is purely a presumption on my part - but the only entity, (the only people) that have access to both every engineering detail of both the transaxle design and the lubrication formulation is Toyota. It is possible that various different formulations of lube can meet the same specification (and can be, perhaps, equally "good".) But, there is only one formulation that was reviewed with the benefit of being able to review the application design details - and that is Toyota's WS. (I'm not saying that did happen, but WS represents the only lube for which it could have happened.)

Use of other fluids (created by manufacturers without the benefit of the application design details) just don't have that same (theoretical) advantage.

All I'm saying is that Toyota knows more about their application than anyone else, and if I'm going to crawl around on my garage floor changing that crap, I want to use the OEM fluid.

I did mine at 15,000 mi & 80,000 mi. In both instances, the fluid coming out looked very clean. I still think it's a good idea (for all the reasons already articulated by Frodoz) to have a regular change interval.

 

Lowly - that's pretty high in my opinion - some of the smartest & most capable people I know are mechanics.

 

Our service manager calls them "techs", hate the term.