ATF fluid changes ARE Required.

Ok. Doug wants to use an alternate fluid, for a few 100 miles, then drain again and refill with Toyota ATF-WS. Is this other fluid even cheaper? And the double drain is needed why?

 

Part of the confabulation might be the absolute silence from Toyota, regarding what to use. At least I've found nothing so far.

They don't even say the transmission needs a change. I just searched the Repair Manual for the string "atf-ws", with no results. There is a description of the change, but the fluid is only described as "hybrid transaxle fluid".

Anyone have a Toyota document with mention of ATF-WS? I think there is something, but not sure.

 

It says WS in the owners manual.

 

Thanks for chiming in. 2 follow up questions, what do you consider to be a "known compatible" fluid, and are you recommending changing the ATF every 5000ish miles?

Doug

 

From the Owner's Manual:
Transmission fluid type
Fluid capacity
* 3.5 qt. (3.3 L, 2.9 Imp.qt.)

Fluid type Toyota Genuine ATF WS
Using transmission fluid other than “Toyota Genuine ATF WS” may cause
ultimately damage the transmission of your vehicle.

If this is not documentation enough I do not know what else anyone may need.

 

Where? I'm not being argumentative; can't even find the word "transaxle" in the owners manual.

Hang on, will try to find jdcollins5's clip.

Bingo: page 563.

My 2 cents: unless you're a mechanical engineer and/or don't mind risking your transaxle or warranty, use the recommended fluid.

Considering there might not even be a cost saving, it's a bit of a head shaker why you'd want to use anything else.

 

Look under specifications, near the back.

 

Doug,

My recommended interval is a first ATF exchange at 30k miles and then every 60k miles thereafter based on my lab tests of used Type WS fluid at 60k mile intervals. Others have looked at the data and chosen a more conservative 15k mile first exchange and then every 30k miles thereafter, but I judge even that to be overkill.

Several PCers are choosing to use Redline D4 or D6 instead of Toyota Type WS, but I will reserve judgement on those till I see lab tests and long HSD life (My 2004 Prius HSD is now at 236k miles).

JeffD

 

In the owners manual as others have said.

Nice catch on it not being in the Prius Repair Manual. The closest I could come to finding it there was "Hybrid Transaxle Fluid" which says approximately nothing

OTOH, they don't specify engine oil either. Could be because the repair manual covers more than one country and they recommend different oils for different countries depending on that countries regulations and what is generally available in their market. It's not uncommon for repair manuals to defer to owners manual and lube charts for lube specs.

 

Here is a Toyota document that I have saved that lists the fluid specifications for all 2010 MY Toyotas.

 

Only for those sold in two North American countries.

 

Does anyone on here have a similar document for other countries for comparison ?

 

The Owner's Manual most certainly does specify to use ATF WS and specifically states using anything else can damage the transmission, on page 563 if you want to read it for yourself. You are correct that there is no recommendation to change.

I do not think anyone in this thread is disagreeing on the need to change, only the correct fluid to use. You are welcome to experiment with your personal car but I for one will only use ATF WS in mine.

 

My guess is Toyota did some kind of study and based on the results, the benefits of early changes were too small to measure or recommend routine changes in most of the cars. Maybe Bob can chime in on this, but I saw results of UOA of factory fluid at 360,000 miles in one of his files. So, that proves that tranny without fluid changes can reach super long life.

I do admit exceptions are possible. UOA the OP showed did concern me a bit. I see some indications of abnormal wear due to large particle sizes. The particles smaller than 20um are normal and harmless. The "wear particles" we see on the cheap UOAs are under 10um and totally harmless.

This discussion is not unlike the never ending argument for first engine oil change. Some like it at 1000 miles or below, some are OK waiting 10,000 miles.

For the record, I did 10,000 mile first engine oil change and 22,000 mile first transaxle fluid change.

 

For what it's worth...

In Doug's situation, it is common industry practice to double drain and fill, minimum, when fluids are known to be contaminated and/or the duty cycle has been exceeded (same thing), to more completely clean the system. I learned using 500 miles between from experience. This is to stop further wear and damage caused by residual contamination and is "usually" adequate. Reset it in other words. For units with removable pans, it is also wise to remove and routinely clean them of the coating/metal/sludge that does accumulate (oil pans too). This is why the "Transmission Flush at Jiffy Lube", where they hook the hoses up, is not recommended on your traditional Ford or Chevy, as it stirs the crud back up into the system, ultimately causing more problems.

The logic not to use a "cheap fluid", my comment referring to quality and compatibility, should be obvious. Although there is indication some alternative ATFs may be suitable, the point is mute if you just change it using the recommended, BEFORE it is "past it prime". This applies to all of your vehicles fluids, filters, belts, ect... That is what we call.....preventative maintenance.

I have always changed my oil at 5000 miles with this Prius, and have since included the ATF to this regiment. After what I learned and saw here, then proved to myself, it became a no brainer. Whether you feel this is excessive is of no importance to me, as this is my car. As mentioned before, I pay less to do both than most, who don't turn a wrench, pay to have just the oil/filter changed alone. And it is done correctly. For those that change, or have their oil/filter changed at 10K, I recommend you do the same with the ATF. Take my advice.....or not....but I am qualified.

By the way, Kudos to the OP on the magnetic drain plug, as they should be used in all such applications and on all vehicles.

 

It's one thing to do obsessive over maintenance and then another to recommend it.