I've been reading through the maintenance guide of my 2011 prius, and there is no mention about changing the transmission oil at any point. It only suggests "inspecting", and checking for leaks every 30,000 miles. That's it. The obvious implication is that it doesn't require changing. It sounds like a classic case of Toyota saying, "if it's not broke, don't fix it." Btw, I bought my 2011 used in 2014 with 32k miles on it. Today, 10 years later, it has a tad over 88k.
If you don't want it to break, change it! They consider it "lifetime" fluid. Which means until the warranty expires. It's easy and inexpensive to change. And well worth it. ONLY use Toyota fluid!
Yes it does sound like that only problem I have with that whole business is every time I inspect one the fluid is all dark brown almost black and it was red when it went in you know lifetime whose lifetime what lifetime oh the Toyota projected lifetime well they want you to buy a new car every 4 to 5 years so that's lifetime to them I'm guessing lifetime to them is when you blow it up and come looking to buy a new one hopefully sooner than later for them. Same with the HV battery lifetime whose lifetime. So if it's my vehicle and I just got hold of it and the ones I get generally have very high mileage I like them that way that means people have had to keep them up to make that high mileage generally speaking lot of times when I pick these things up out of these places and tow lots and whatnot people have done all kinds of work in the next project is just worn them out and they lost interest and bought a yaris or a Chevrolet truck. So I just step in and do what they didn't want to and off we go I personally wouldn't want to be driving around with the fluid looking that ugly oil or CVT fluid That's just me personally some people will never even look and most of those kinds of folks are out of the cars much faster than I they have other things that they have to keep up with neighbors and fancy neighborhoods and all that sort of thing You're enough peer pressure you'll change your car just because whatever.. I think that's what happens with Prius people buy them have lots of some kind of expectations and then they realize maybe not and they're off to the next thing very short attention spans that sort of thing.
Folks on PriusChat did lab analysis on ATF fluid via Blackstone and the conclusion is changing it at least once will reduce wear & tear, but changing more often than that wouldn't make much difference. Toyota's opinion is the ATF is good for the life of the vehicle, but the shorter the lifespan of the vehicle, the more profitable it is for them. That's also why scientific analysis by PriusChat DIYers is awesome!
I wish they had did an analysis of The Magic of Only Toyota ATF. Surely there has to be a more affordable solution.
For me, a DIY drain-and-fill, with Toyota ATF WS and replacement washers for the fill/drain bolts, cost about $50 CDN (plus sales tax).
Here in Torrance (Los Angeles county), it was $68.23 (total, including tax) at the dealer. It was the same price no matter which dealer I called. This did not include the crush washers which I bought from Amazon for $8.99 for 10 of them. Amazon also sells the ATF WS for a just under $58 for 4 quarts, but with tax it's about the same as the dealer.
That was parts department charge, for four quarts, in US funds? Admittedly my last purchase was in September of 2016, and with “supply chain” issues it’s likely gone up, but I got liters of ATF WS for $9.14, and the washers for (userious) $3.80 apiece, all prices CDN. Doing the math for 4 liters fluid and 2 washers, works out to $32.68 in USD. Again, thats September 2016, likely higher now.
