ATF fluid changes ARE Required.

+1. Mobil 1 ATF doesn't meet the Toyota-WS specification. (There are few which do, and they include Toyota's own, a Redline product, and an Eneos product).

 

Where can we find the Toyota Specification that you cite?

Thank you!

 

To Bill (OP),
did i read the UOA correctly the WS viscosity was 12 cSt@100C? This is totally insane and the only way I can explain it was thick from metal particles. IMHO, this UOA is showing accelerated wear in your transaxle. Was the ATF level correct? Any history of accidents or major repairs? Any noises? Any high speed driving? Any grill blocking?

Now, coming back to the WS as being the best possible fluid, it's best for fuel economy but not necessarily for wear protection. To this day I have a pdf document issued by Toyota in early 2000's that stated that WS ATF allows for superior fuel efficiency while providing "acceptable" wear protection.

 

Nice catch, I missed the viscosity.

Bill, do you know for sure that the car had WS in it when you changed it at 112k miles?
It looks like either someone put the wrong oil in it or the test was wrong.

 

What's your point? That JASO 1-A is equivalent to Toyota WS? I'll agree this is quite possible, and there is plenty of discussion of the specifications over on bobistheoilguy.com.

My point is that the ATF called for in my Prius is specified to satisfy Toyota WS. That's what I'll be using, and what I used when I drained and filled my unit at 30,000 miles.

 

Looking at the additive pack, looks very similar to the other WS samples. Other brands have slightly different additive levels.

 

The metallic particles at 420 miles after your ATF refresh are due to the fact that there is still some ATF lurking in the Tranny after a drain. You are just diluting that old ATF with the fresh fill. This does not indicate continuing wear.

JeffD

 

That's an interesting puzzle. I have seen a few oil analyses on cars with around 60k miles and the oil has sheared to a lower viscosity. I haven't seen any UOAs on Prii with over 100k on the oil but would be surprised if the WS got that much thicker.

 

Not that I agree, but here is Toyota's statement:

 

There is plenty to disagree with Thanks for posting it though, even if we don't agree with all of it, it's always a good thing to know what the business/marketing arm's highly filtered version of what the Mothership's engineering is saying.

One of the errors in that document significant to us is the 100,000 miles inspection interval. The warranty/maintenance schedule on my 2010 says every 30,000 miles. In case anyone is wondering, in the Toyota shop manual, "inspections" only consists of checking the level. No sniff, visual or lab tests.

A really fine bypass filter on the transmission would be nice but that would require a pump and with the transmission typically lasting well beyond the first owners time with the car. It wouldn't make bean counter sense to the manufacturer. They are probably right, if everyone's pet project was included by the factory a Prius would cost $80,000 and weigh 4000 pounds.

 

I can't explain why the viscosity is twice the normal thickness, but I'm not a fan of alleged "lifetime fluids." I would have been frightened, too, seeing iron at 391, aluminum at 392, and silicon at 154. Don't worry about the particle counts, which are notoriously inaccurate. I'm not worried by the M1 ATF, either, since it's within 2 cSt of the Toyota WS.

 

There is a lot more to fluid than kinetic viscosity. Additive package is the most important.

 

Bill,

Welcome to PriusChat!!! I believe you will find the forum a very valuable tool to place in your toolbox throughout your Prii ownership experience, I know I have. Unfortunately one of the issues with there now being so many different models in the Prii Family is not all the information is listed in every forum. A lot of the information you are asking about has been posted in the Gen II Forums since 2007.

I am a firm believer in regular ATF changes and do them every 50,000 miles now. My next Prii will have a drain and fill at 5,000 miles then again at 20,000 miles then 50,000 miles and every 50,000 after that.
A couple of sticky's from the Gen II forums:

Transaxle Oil Analysis | PriusChat

DRAFT Transaxle Oil Testing Results | PriusChat

I hope this information is useful. The "Search" function is very useful and can lead to other finds and reports on things such as tires, headlights and the such. Welcome again to PriusChat!!!

Happy driving,
Chris

 

Bill,

See: What services you need and what you don't | Page 34 | PriusChat

It cover most of the maintenance issues although I don't always agree with the OP on the advisability of periodic ATF refreshes.

JeffD

 

Yes, but most of the useful info is in the OPs first post in that thread and it is a "Sticky".

JeffD

 

When I saw the subject of this thread, I thought 'Good deal, Toyota finally saw the light.' It is Christmas Eve and I finally read the full thread. I love yo' all but gosh . . . I'd like to offer some thoughts:

• 5000 mi ZVW30 transaxle change - I also ordered a particulate analysis and was surprised at the size and quantity of particulate matter in the sample. I understand that manufacturing debris might be in the oil but the amount of sealant debris was an order of magnitude higher than I expected.
• quality of Type WS - the closest I could find (and I LOOKED!) was aircraft turbine oil and they were slightly less than Type WS. I am planning to fly behind a two-stroke, oil injected engine and if the ash level of Type WS beats the best recommended two-stroke oil, I'm flying Type WS . . . and my airplane is on the line.
• additives - there is a distinct lack of moly in both Type T-IV and Type WS and that suggests it should be avoided in transmissions that have 300-600+ V electrical potentials. Only transformer oils have compatible moly levels ... none.

I wish I could find a better transaxle oil than Type WS but I have failed. If someone wants to use something else, I have no problem but no interest until:

• perform cold weather roll-down test
• provide a full spectrum oil analysis both virgin and after 7k service miles

I can be pursaded by credible facts and data. However, I am immune to marketing BS . . . because I will send samples to my oil testing service.

Bob Wilson

 

When we Prius drivers back up, we really don't go in reverse. The mfd shows going backwards, in reality the Prius stands still and the scenery around it moves forward.

DBCassidy