WS ATF Question

Toyota WS is the ONLY ATF that is certified for use in the current Prius (an experiment with Amsoil ATF FAILED in a classic Prius - excessive copper in the used fluid). Note that the electric motor windings are exposed to the ATF and you don't want to have any material interactions that will shorten the life of your Tranny. Plan on replacing (not flushing) the ATF every 60,000 miles as this has been shown to be appropriate by laboratory testing of used ATF. You can do it yourself, but dealers will charge less than $100 for the job which is less than 0.2 cents per mile.

JeffD

 

The 2001-03 model NHW11 uses Type T-IV, which has similar characteristics to Amsoil ATF (NOT RECOMMENDED.) I tried Amsoil and found a substantial increase in copper in the subsequent oil changes and tests. Because of this, I can not recommend Amsoil ATF even though it appears to maintain viscosity better than Type T-IV. I suspect some of the additives in Amsoil ATF may accelerate wear.

I have not looked for an alternative to Type WS, which I am testing in my NHW11 transmission. The reason is I don't have a good way to test the additives to make sure they don't attack the wiring and insulation of the transaxle.

Unlike ordinary mechanical transmissions, ours have two, powerful motor-generators. Our transmission has more in common with large transformers than an ordinary, mechanical transmission. So this means we have to be sensitive to break-down voltages and the effects on wire insulation.

Bob Wilson

 

Another good reason to do an early initial change at around 16,000 km, then every 36,000 km or so.

My dealer charges me $22 for a 4 litre tin of WS fluid. It's cheap insurance. Takes me around 25 mins to drain and refill, and that includes trying to keep the cats from sitting on my face while I'm under the car

 

Related question....
I plan on replacing the Type IV ATF in my classic with the WS formula.
I read that a funnel with a long extension (like 2-3 feet) of flexible tubing works best to refill from the fill point underneath the car. What size tubing would work best? Meaning inner diameter of the tubing... 3/8", 1/2", etc.
Thanks!

 

Thanks for bring this topic up as well, looks like Toyota's ATF-WS is the only fluid to go.
As for the CVT fluid change, can someone post the Torque-number for tightening the Drain and Refill nuts?

 

This might help:
2003 Prius - Cold Weather and Transaxle

The filler and drain plug are identical, 24 mm. I'd recommend 3/8" since if the hose is too large, it won't fit in the hole. Also, I recommend getting a transaxle pan gasket and cleaning it and inspecting the debris.

We are finding evidence that the transaxle case sealant ages and parts fall off and collect in the pan. Removing them from the pan makes sense.

How many miles on the car? How many miles on this transaxle fluid?

You don't have to test the oil but if you have a capture bottle, a clean, dry polycarbonate or polyethelyne container, you will have the option.

Bob Wilson

 

29 ft-lbs (39 N m) for both the drain and fill ports for the NHW-20.

I was able to buy WS ATF for $5.20 / qt at a local Toyota dealer. The gaskets for the drain and fill were approx $ .80 each, but probably reusable (aluminum washer).

 

Always take off the FILL plug first. If for any reason you can't get the fill plug out, you sure don't want to find out after all the oil has drained

Don't mix up the inverter coolant drain for the cvt fluid drain. The attached photo has arrows indicating the location of the cvt fluid fill and drain. Photo courtesy of Hobbit

 

Thanks for the info, Bob.
My Prius has 121K miles on it. I honestly do not know if the tranny fluid was ever changed. The Passport book only talks about inspecting it....
I am the second owner, you see. I bought the car at 100K miles. Some maintenance was done at the dealership by the first owner. So, for the tranny fluid, there is a checkmark for inspecting the fluid back at 90K miles.
I will try and save a sample and send it for testing.

 

I would like to note here that Toyota T-IV is their only fluid specified for the 2001-2003 Prius. That having been said I had my 2001 Prius changed to Toyota WS a long time ago and it has been perfectly happy. No used fluid analysis on that one yet though. In fact it was well-trusted Toyota tech who agreed with my plan of using WS.

However there are at least a few Prius veterans who regard the use of WS in 2001-2003 Prius as still experimental, and at our own risks. I just wanted to make sure that this pont of view was recorded here.

 

The NHW20 model, 2004-current, does not have a transmission pan. The NHW11, 2001-2003, does have a transmission pan.

Again, testing is not required but if you don't have a sample container handy, testing becomes impossible. Also, it is important to get viscosity measurements at 40C, 100C and the viscosity index. This gives the primary indication of the oil health and status.

Bob Wilson

 

I missed this the first time. Are you sure Amsoil coolant is compatible with the Toyota long life coolant?

 

Thanks for the Torque-Spec info.
Btw, what's the right tool (size?) to unwind these plugs? (They look like Allen bolts)

 

For the NHW-20, the fill plug is a 24mm hex head. The drain plug is a 10 mm recessed hex (allen head).

 

Let me get this straight. The photo posted by Jayman shows the location of the 2003 and up CVT drain and fill plugs. Is that right?

If so, it looks like it is just as easy as draining and filling a manual transmission. How many quarts of fluid do you need?