A couple of WS Alternatives.

4 qts WS ATF @ $5.20 / qt + $0 Shipping (pickup at local dealer) = $20.80 + local sales tax.

 

Let me give you some "blah blah."

The WS fluid in the Prius transmission is bathing electric parts that have 500V or so potential between them. This is because the Prius transmission also contains high power electric motors. Toyota is SURE that their WS fluid is electrically non-conductive.

Having high power electric motors in a transmission is relatively rare (because it's unique to hybrids using the Prius design or similar).

Other transmission fluids might work just fine for protecting the bearings and the gears of the Prius transmission, but might break down electrically near the terminals for the motor coils.

Are you sure that the other fluid manufacturers have formulated and tested their transmission fluid so that it won't ever conduct electrically? I bet an electrical flash-over inside your Prius transmission would just suck!

The Prius puts unique electrical demands on its transmission fluid that conventional cars don't. It has to act both as a transmission fluid AND a transformer oil (electrically non-conductive, no matter how many miles it has on it). This alone suggests to me that it would be wise to play it safe.

 

But you didn't answer the question. Who's being a smart nice person now?
(Sorry about calling you a smart nice person. I just had to point out the irony here.)

 

Their specs say nothing about being compatible with high voltage motor-generator windings. Let us know how it works out for you.

 

I wasn't trying to be a smart nice person.

No, I'm not sure they haven't tested their transmission fluid to determine its high-voltage electrical properties.

If their fluid works, I don't see that you've gained much.

On the other hand, if it's not electrically compatible and your motor generator windings flash over, you'll likely be in a world of hurt.

Toyota would point the finger at the transmission fluid manufacturer, they would point the finger back at Toyota, and you'd be caught in the middle.

Sorry if pointing this sort of stuff out makes me a smart nice person.

 

"might break down electrically"

What??? You must be kidding. How does that happen? Please...stop.

Every time someone discusses WS fluid HERE someone comes up with this dielectric nonsense...oh lookout there's electric motors in there. Which is just stupid. This is not transformer oil. WS is high quality low viscosity atf also used in many other Toyota vehicles ostensibly Tundra trucks. Period.

Do you have any idea how hard the conformal coating is on the exposed motor windings. So hard Toyota Engineers never gave it a second thought that hot ATF would affect that coating.

People come to this great site for facts not ridiculous opinions.

The original poster is absolutely correct. In our case its strictly a question of GL-4 gear lubricant.

I have been running Redline D6 in my 07 for 20K miles now and it runs perfect. Far better than WS fluid. Much smoother & quieter. You get what you pay for.

You want proof that I'm right there's no motor friendly non conducting additive in WS? Whats the WS look like after 40-50K miles. Gettin' pretty dark? That's because there's metal in the fluid. Liquid metal. Lots of it. That is kinda breaking down electrically isn't it? The factory doesn't seem to care about your non conducting issues either as they list WS as a 100,000 mile replacement. Have you seen 100K WS? Its almost black with metal. Get it?

 

Have you done a UOA yet on the D6? I'm wondering how it would compare to the WS fluid. I had a 10k factory fill sample done and another 10k sample after I changed out the initial fill.

I think D6 is also somewhat higher viscosity than WS. Have you noticed any change in FE?

 

But there have been a number of HSD failures in 2001-2003 Prii due to shorted turns in the MGs so there may be an issue here (the 2001-2003 used an earlier ATF formula)

Several of us have posted lab analysis of used Toyota ATF performance

As noted above, there are other issues

See my comment below about break-in, that may account for some of the perceived difference

Toyota doesn't really care how long the HSD lasts past warranty. I do.

Our group of techies have found that 30k is a long interval for the older Toyota ATF and 60k miles is a reasonable period for the 2004-2009 Prius HSD with type WS. My 2004 had significant metallic load in the ATF at 61k miles and a lesser metallic load when changed again at 120k miles (the gears now mesh more smoothly due to use). We'll see how it is at 180k miles in a little over a year from now.

Note that a refresh of Type WS is about $100 at the dealer (I add $25 for lab tests) which about 0.2 cents/mile at 60k intervals (compare to 5 cents/mile for gas - currently, it will go higher). This is a low cost for extending the life of the HSD.

JeffD

 

Hardness has almost nothing to do with solubility. The issue here is whether the winding insulation will eventually dissolve in the ATF. It could take years to dissolve; if it ever does happen you will certainly know it. The dark material you see in the used ATF is metal particles from the gears, not the windings, in suspension. This is a symptom of mechanical wear, not electrical break down or dielectric failure.

Whatever you are using may be fine, but why risk a $2000 repair to save $20 worth of fluid?

 

Let me think?

Toyota spent millions developing a unique car we all love.
They spent countless man hours on ensuring the car was reliable, after all their reputation rides on it.
Toyota recommends WS trans fluid.

I have a HSD trans-axle in my Prius which would cost about $8,000 to replace if it broke.
In the 300,000 kilometres I will likely do in this Prius I'll do 2 trans oil changes, one at 100,000km (done already) and one at 200,000km, not at 300,000km, that will be the new owner's problem.
WS oil costs $40 Australian so I will spend $80 on transmission oil for my Prius using the oil recommended by Toyota.

Or I could use an unspecified oil for $25 a change saving $30 over the time I own the car.

Lets weigh up the risk benefit.
$30 saved(benefit) versus $8,000 transmission replacement I am risking.
Cost saving to cost risk ratio = 266.66 to 1

I think I'll use WS, you are free to use what ever you choose but if your transmission fails please don't be shy and tell the world you are crying because the transmission of your Prius failed costing $8,000 but you saved $30 by using a cheaper transmission fluid to that which Toyota recommended. Please don't blame Toyota if your transmission fails.

 

As far as the debate over dealership WS vs "comparable" substitutes, I guess a lot depends on your pucker factor.

WS fluid is fairly universal now in the Toyota lineup. My FJ uses it as it has a 5 speed auto transmission. I can get a 4 litre tin of WS for $22 at my dealership

Comparable substitutes may cost just as much, if not more.

When it comes to oil, I've never fallen for saving a few bucks at the expense of a major repair down the road. What I find odd is that the US market Prius has no set fluid replacement for the transaxle, but the Canadian market Prius *does*

IMHO the most benefit to changing the transaxle fluid would be fairly early, say 8,000-16,000 km initially. I noticed when I did the first change, the fluid was already a very dark red. Subsequent fluid changes, it remained clean

If you're not anal about looking after equipment, then don't worry about the fluid. Some of us are pretty anal, I've been known to regularly change power steering fluid on other vehicles.

Amsoil has also announced a WS alternative, should be out in May/June timeframe. The cost will likely exceed what the dealership charges for genuine WS

 

If I use 4 liters of the genuine WS for $22, I'm very confident that the fluid is electrically compatible.

If I use 4 liters of something else less expensive (even if it's free), I don't know about its electrical properties. I've not seen that anyone specifies them in their fluid. So, if it happens to be a bad dielectric, it still meets their stated spec. But, it could damage the Prius motor-generators.

I'd rather play it safe because the potential cost is so much more than any potential savings on $22 worth of WS fluid.

This issue comes up because the Prius places electrical demands on the fluid that almost no other car does.

Let's say a new Prius transmission costs ~$8k, and the probability of another fluid ruining the transmission (because of electrical incompatibility) is about 1/2 of 1%.

The expected cost of that risk is 0.005 x $8k = $40 bucks.

Am I 99.5% sure that another transmission fluid, never designed, intended, or tested for its electrical properties, will work fine in the Prius? Nope.

Therefore, *I* can't afford the risk.

Will it work? Probably.

Do *I* want to assume the risk that it won't? Nope.

 

Precisely

Even if the electrical properties of the fluid are a non-issue, there could be other things going on inside the transaxle. A lot of folks are not aware that a chain is used to transfer power to the differential. This is similar to the chain in a four wheel drive transfer case

What if something goes haywire with the chain? Either way, CRUNCH and you've ruined a fairly expensive component. We've had a forum member - dailyphotofix - replace the entire assembly after the mechanical parts quit. He's very handy mechanically, I doubt it's a job for the average shadetree mechanic

I'll use substitutes when I'm willing to accept the risk, and understand if there are any benefits to doing so. Eg engine oil, I'll use a synthetic but one not of the "recommended" viscosity, as the same motor used in Europe and Australia has a different viscosity recommendation

Or say the power steering system in my FJ. The factory fill is some honey-color stuff that seems to break down fairly easy. I recently did a complete fluid exchange on my FJ power steering to Amsoil "universal" ATF

If the WS fluid was just for the Prius, and cost say $50 a litre, I'd probably consider an alternative. Since the WS is priced very competitively to other fluids claiming to be compatible, why not just use the correct fluid??

 

The dark material is of course gear wear metal in the ATF .... not winding material. I never said it was from winding material. Thats crazy.Why do you infer I said that. That kind of goes against my whole argument. My whole point is and let me put it in caps for you :

HOW CAN THE WS FLUID HAVE DIELECTRIC PROPERTIES IF ITS FULL OF METAL IN SOLUTION FROM GEAR WEAR METAL AFTER 50K MILES OF USE?
YOU KNOW...GEAR WEAR...THE STUFF THAT'S MAKE THE FLUID DARK...AND SINCE ITS NOW A METAL IN SOLUTION ITS NOW A PRETTY VOLTAGE CONDUCTING FLUID. VERY CONDUCTIVE. AS IN HAVING NO MIRACLE DIELECTRIC PROPERTIES.

BESIDES:
If you have ever been inside an automatic transmission there's lots of plain old just plain wires and flimsy plastic parts subjected to very hot ATF. You should see all the wires in my Crown Vic PI trans pan. ATF is not very caustic or harmful to even wires much less hardened motor windings. It ain't battery acid dude. It just not an issue.
So I guess your point is there's another miracle additive in addition to its miracle dielectric properties that's makes it non soluble to conformal coating. This is turning out to be some fluid.

And to wind it up I did not say to use any other fluid other than WS. I happen to use another brand and it works fine. I never said once don't use WS. WS works fine. I happen to use a product I think out performs it.
The original poster is correct to in that there's alot of other brands that will also work.

Its just transmission fluid.

All I'm saying and all I have ever said is stop with the miracle additive dielectric properties its a special electrical fluid crap. Its ridiculous and very confusing to people who come here for correct info.

 

yes I lost about 1 mpg but its significantly quieter and smoother.
Just like all my other cars. I have leveled out to about lifetime 48 mpg's but I rarely hypermill.

 

Your quote:

"Prius places electrical demands on its fluid" ? Really...Please...do tell. What are these demands?