ATF fluid changes ARE Required.

I bought a spare plug and drilled two holes for the heat shrink covered thermistor. I calibrated it using steam and an ice water bath. Then I ran the leads into the cabin. I have photos on my web page.

Bob Wilson

 

My original goal was to reduce rolling friction by reducing tire flex. Then I found it significantly improved straight line stability.

First get one, lowest rev/mile tire and mount it on a full size rim. Test the tire on one rear wheel in worst case like speed bumps at higher speeds. If it passes, buy a second and mount both on the front. You may notice the attitude change but if it doesn't cause a problem, you are done.

You will have to use calibration constant or go GPS for speed and distance.

Bob Wilson

 

Bill, the wisdom if the internet says that WS is more hygroscopic (moisture loving) than normal transmission oil. I share your concern even though Bob hasn't seen any adverse results yet.

 

Here's a thought.

Where I bought my car, the parts dept. charges $45.64 for the recommended Toyota oil and filter. For the WS ATF fluid it is $40.40. So doing the work yourself and changing both at the same time, say every 10K miles, that's $86.04 after tax. IF you need fill/drain seals appx $15 more. Still less than what the average Dealer charges just to change the oil/filter for you every 10K miles. And I'll just bet someone here knows where there are better prices.

hum...

 

Hi Bill,

Use the "Rev/mile" as that is the only true metric. The aspect ratio can be misleading.

There is no adjustment for the speedometer or trip meter. So I simply measure the offset and do the calculation in my head. A spreadsheet works just as well. <GRINS>

So far, none of my oil sample tests have shown any evidence of water in any measurable amounts. That may change in the future but until then, I'll keep my setup.

Bob Wilson

 

Thank you for doing that and keeping us informed.

 

Pretty please?

 

Okay, not sure this is the best place for this but here goes. I have never changed the transaxle fluid, trusting the service manual and assuming "check it" was pretty much meaningless. I just ticked over 100K last night and want to change the fluid soon. Based on reading this, I am thinking it might be a good idea to drain it, refill, run 1K miles or so, drain and refill again. I don't really want to drain anything "good" after 1K miles and I am now completely out of any warranty. It seems to me that it is a reasonable "risk" to run Supertech Dexron VI for that short period of time, then drain and replace with either Toyota WS or Redline. Since I don't see doing particularly frequent changes, it seems to me like Redline D-6 probably holds up better but I am not sure which I would use. Thanks, Doug

 

Thanks Bill, I guess I am not that into it

In your opinion, nothing horrible will happen running "cheap stuff" for a short time? Seems like a good idea to clean things out and I don't mind wasting my labor but I don't like wasting my moolah.

Doug

 

I would not ever put any "cheap" ATF in my Prius as a percentage of it will live on after further drains and refills.

JeffD

 

I'm not sure about second gen (per your signature), but just assuming the spec'd. transaxle fluid for yours is the same:

Toyota ATF-WS was $9.32 per liter when I purchased about a year back. If Toyota tells me I need to be using a specific fluid, there's no way I would throw something else in.

Even for a short duration, I would not want to contaminate the transaxle with something else. Also, I don't see the logic in double change. For one thing, the drain is very complete, not like a regular automatic transmission, that retains maybe 50%.

My 2 cents, if you want to do a double change, use the kosher stuff both times.

 

So are you suggesting that more like 500 miles then drain the Supertech? That works too.

I didn't realize I had landed in a GenIII area until you pointed it out I guess at 7YO and now 100K miles I am not concerned about babying the car. Seems to me that low mileage Supertech Dexron VI is less of a contaminant than original fill Toyota ATF WS with 100K miles on it. Plus, if it is a nearly complete drain like a manual transmission it doesn't seem like contamination is a big issue.

Thanks, Doug

 

If you go to the page 1 of this thread and look at the OP's UOA, you will see roughly 10% contamination rate. I don't think what you plan to do will be harmful to the tranny, but it's not exactly proper.

While I replaced mine at 22,000 mile mark and I'm glad I did for a peace of mind, I'm still not entirely convinced one absolutely has to do it very early on. IIRC, Bob posted UOA from factory fluid at 350,000 miles, so long life is possible with old fluid too. Based on my analysis of posted UOA, there is some weak evidence that change at or before 60,000 decreased wear SLIGHTLY as opposed to waiting 100,000 miles.

So what I'm saying, you are better off doing it every 60,000 miles rather than doing it twice at 100,000 miles.

 

I am going to speak as a Mechanic, not as an Engineer, internet search wizard, couch potato or any other kind of self professed expert.

To Doug (dvancleve). After 100K miles on the original ATF, do a double drain and fill with the factory recommended fluid. The initial, and again after 500 mile of normal driving. Do not use the "cheap stuff". With that many miles you are just asking for trouble, I don't care what you drive.

To the other interested parties. Whether you use WS or another known compatible quality ATF, the point is change it and stop talking about how smart you are. Who has the longest xxxx or prettier wife has nothing to do with maintenance, preventative or repair. My educated and experienced advice is to change your Prius ATF when you change your oil/filter. It doesn't take a rocket scientist to know when fluid is past it's prime. Found my last actual receipt for $92.24, which included all needed for this including the washers/seals. $46.44 for the trans, $45.80 for the motor, just in case you missed the point earlier.

This is needed preventative maintenance people and I dare any qualified Mechanic (Toyota, NASA, Jose or Joe Bob), to say otherwise. Take care of your vehicle, what ever it is, and it will take care of you and yours.