Transmission fluid

welcome!
no, it is considered 'lifetime' by toyota. however, if you plan to keep it more than 15 - 200,000 miles, some here consider it a good idea based on oil evaluation lab testing. some recommend every 30k, and others, at 5k, then every 30 or 60. there are no definitive guidelines, because no one has done long term testing. all the best!

 

The "official" Toyota answer is no! However, its difficult to believe that a fluid will provide the same protection for the entire life of the car. I change my transaxle fluid every 60,000 miles. It might be overkill but if you think about it, there is no cheaper insurance. When you consider the cost of a new transaxle, the $100 that I have spent between both fluid changes is pocket money. You should also take into consideration your driving style. If you do normal commuting then you might be ok. I myself punish my car every single minute I am driving it. Let's just say I stay in power mode for most of my commute. I also take frequent road trips across the country and Canada. For me I feel its worth it and like I said, it is a cheap insurance which gives me peace of mind.

BTW- If there is something that Toyota did right with the Prius, it was the procedure for the changing the transaxle fluid. It is one of the easiest DIY jobs in any car I have had. You should see the 12 page TSB for checking the transmission fluid level on a modern Camry. Just make sure you buy a set of the plastic clips that hold the underbody tray in place. I managed to break most of them because of how brittle they get with age.

 

See my response here:

Transaxle Fluid - 160k | PriusChat

I also do all my own oil changes, maybe 12 so far, take the engine under panel off each time, and have yet to need a replacement fastener. What kills them is grit in the mechanism: take the panel off occasionally, wash all the fasteners in hot soapy water, work the mechanism, they will not jam up, will be like new. Note: there are two of the plastic fasteners that are a bit bigger (at the "oil flap"), they have grey heads.

 

I think that the main reason that there are questions about changing the transaxle fluid on a Prius is because the Prius transaxle is much simpler than a conventional automatic transmission. I smirk when I see that AAMCO TV commercial where they have the exploded view of the "800 parts" in automatic transmission. In a conventional automatic transmission, the fluid is used to transmit power in the torque converter, and there are numerous gear shifting parts and clutches. In the Prius transaxle prior to the Prime, all the parts are permanently connected together. The Prime has introduced one clutch to enable both motor generators to apply power to the wheels. Yes, if you look at the fluid in a Prius with 60,000 miles, you will find a lot of crud. But there is debate whether that will have any effect on the longevity of the transaxle.You will find people who feel strongly about this on both sides. I don't have the mechanical expertise to offer a knowledgeable opinion on this.

 

I can't invest in a debate over whether or not to do a trivial chore, something on par in expense and time, with an oil change. I did a first transaxle fluid change around 15K (km's). The drained fluid looked quite dark compared to new. I did a second change around 40K: the drained fluid was actually look pretty good. I recently did a third change around 62K, swore that was it for a while: the drain stuff looked like new.

But yeah, simple cheap, why not?