Transmission fluid

You want Toyota TE fluid.

Priuses before 2023 used WS. Starting in 2023(gen5), they now use TE.

You should be able to easily go 6y/60k miles between changes. When you do need to change it, you'll need a jug of this:
E-Taf,Te
The capacity of the transaxle is about 3.7L, so a single 4L jug should do you.

You'll also need two of these(one for the fill and one for the drain):
Gasket #9043018008 | Autoparts.toyota.com
Always replace plug gaskets when changing fluids.

 

Except this on page 522 of the Owner's Manual:



And if you're changing it yourself:

 

The simple answer is that both are correct, but for different reasons.
1. Toyota's Lifetime fluid, I interpret it's as Toyota is no longer obligated to warranty the unit. Their "bean counters" has determined that fluid has a 95% chance of lasting the 150K miles warranty mandated by CARB states.
2. Those of us that has done ATF changes can verify that fluid gets dirty around 15K-20K in service. It makes sense since there's break-in and initial gear wear. While the transaxle doesn't undergo the harsh environment of an engine; there is wear, contamination, and chemical break-down of that fluid over time. We believe that dumping out the ATF after break-in would be prudent. Cheap insurance....

I've personally done two ATF changes in my old Prius C, before it got totaled out. The second change, around 90K miles, the ATF was much cleaner than the first original ATF change at 20K miles.

Hope this helps.....

FWIW; Subaru has the same approach. Strangely though, there's a footnote in the maintenance manual that states towing and 'under extreme conditions', the ATF should be changed at 25K mile intervals. Well my sister has 135K miles on hers and it started to intermittently slip for about 2 seconds randomly. I was out there on vacation and diagnosed it. All maintenance services was performed at the dealership. She's on really good terms with her service advisor; so I played 'bad cop' and nailed them down to 'going off pavement is considered extreme conditions.' Told him my sister's driveway is a mile long gravel road and do you ask any of your customers if they leave the pavement? Ahh; it a Subaru - why do people buy these cars? They did a 'complementary', customer satisfaction, brand new replacement and gave her a free loaner for the 3 weeks it took to get done. I think there's also a pending class action lawsuit on that issue, which made it easier to get that outcome.

 

I've been thinking about this for the last week or two. Why the initial fluid gets dark early but later changes don't in a low-wear unit like the eCVT. I'm starting to think it's just byproducts of the aluminum housing reacting with the fluid. Over time, a boundary layer forms over the metal and the new fluid stops being able to interact with it. Different mechanism but same effect as seasoning a cast iron pan with oil.

The question is whether the byproducts affect the performance of the fluid at all. It's very possible it's only a cosmetic change and the performance of the fluid doesn't change. The only thing the fluid really does is lubricate the planetary gear set. It doesn't have to do anything near the same amount of work as in a regular CVT or automatic transmission.

Unless someone can show me hard data that the fluid's performance actually changes significantly after the first 15k-20k miles in an eCVT, I'm going to stick with my plan for either 6y/60k or 7y/70k.

 

The heating and cooling cycles of the fluid will eventually break-down, effect the performance characteristics of the fluid. I don't have any data on that, but it's a well known fact that heat plays a major role in a fluid's chemical structure. It would be helpful, if someone doing their first ATF change, say about or beyond 150K - would send their ATF out for analyst.

 

Yeah, but an eCVT is a completely different animal than a standard automatic transmission. You can't use old wisdom gained from experience with them on a new system that uses completely different principles.

An typical automatic transmission uses clutch packs that have dozens of individual friction discs that engage and disengage under load. It's that friction that creates the heat that necessitates transmission coolers and can breakdown ATF. The friction material on those discs can also break away and contaminate the fluid. (which eventually leads to the reason you never want to do a first fluid change on an automatic transmission with over 100k miles) In the case of an automatic transmission, an early fluid change is not a bad idea because you get rid of any loose friction material that got knocked off during the initial wear-in. You also get rid of any metallic debris from the metal parts mating together(same reason as doing your first engine oil change at 500-1000 miles)

In a transfer case or differential, an early change is a good idea because of the mating of the metal parts. See the Car Care Nut's recent video on his Lexus GX460 where he changes the transfer case and diff fluids in his GX that's only 2.5 years old with 20k miles. That stuff was UGLY(but normal).

But none of that applies to the eCVTs in most Toyota hybrids. There are no clutch packs or friction discs creating significant heat. The planetary gear set at the heart of the unit is small and doesn't create nearly the wear-in debris that a diff or transfer case does. Besides, the two motor-generators(MG1 & MG2) create far more powerful magnetic fields than any little magnet on a drain plug. I have to believe any metal debris gets pulled out of the fluid immediately and sticks to the MG housings. So if there's no metal debris in the fluid, no friction material in the fluid, and no significant heat from friction discs, is there any real need to do an early change just due to color(which might just be cosmetic)?

 

The gen 1 transaxle had a removable pan with a magnet in it. Mine had attracted a pretty thick coat of metal silt. For whatever reason, it doesn't all seem to stick to the MG rotors.

 

It seems the original poster had a FWD, but the rear trans on the AWD uses the same stuff.

 

Correct. If you have an AWD, you get the joy of having to buy TWO jugs of TE and throwing out most of the second jug.

I'm soooo looking forward to that. /s

 

Brings up a point: I did find a Toyota document regarding Toyota ATF-WS (transaxle fluid for gen 2~4), saying to only use fluid from newly opened bottles. Perhaps applicable to the new fluid as well?

funny thing, it was some sorta white paper on ATF-WS, and this is NOT noted in repair manual. What IS noted, and the writers go to increasingly Byzantine lengths about it with each successive generation, is temporary reinstall of fill cap, I think mechanics would mostly ignore this, just do the job fast.

and likely goes without saying, but presumably “throwing out” involves recycling.

Which brings up another point: sometimes engine oil recyclers balk at accepting the more exotic fluids, good to check. The last thing you want is to bring something to them, and it ends up poured out round back.