Transaxle Oil Analysis

So where should I post the results of my transaxle oil test? I replaced the transaxle oil at 5,000 miles and sent a sample off to Blackstone for analysis. The results came back and in the spirit of sharing, I am ready to post the results. But where?

Edit: What the heck, I am posting the results here and the mods can move/copy to wherever. If it is moved, I would appreciate a PM of where it was moved to.

COMMENTS: Universal averages for this type of system are based on an oil run of ~15,000 miles. The high wear and silicon that we found are common finds in new transmissions. The excess wear is from new parts breaking-in, while silicon is from sand-casted parts and sealers used when assembling your engine. Both should improve with subsequent oil changes. Insolubles were high at 0.2%, so it was definitely time to change this oil. The TAN read 1.0, so this oil was fairly acidic.

ELEMENTS IN PARTS PER MILLION (1st column is the sample results, 2nd column is universal averages for comparison)
Aluminum........17...16
Chromium.........2.....1
Iron................54...38 (Probably break-in particles)
Copper..............7...51
Lead.................1...10
Tin...................2.....2
Molybdenum......0.....1
Nickel...............2.....1
Manganese........4.....2
Silver...............0.....0
Titanium...........0.....0
Potassium.........0.....1
Boron..............61...55
Silicon...........140...50 (As the comments noted, high in Silicon)
Sodium.............2.....4
Calcium.........126..130
Magnesium........2...19
Phosphorus.....276..284
Zinc..................4...57
Barium.............22....8

PHYSICAL PROPERTIES (1st column is my sample results; 2nd column is where the sample should be)

SUS Viscosity.....43.3......42 - 51
cSt Viscosity........5.21......4.8 - 7.9
Flashpoint - F....375.....>335
Fuel %................-
Antifreeze %........-
Water %.............0.0...<0.1
Insolubles %........0.2...<0.1
TAN....................1.0

Net,net, net I am glad I replaced the transaxle oil at the 5,000 mile mark. Whether anyone else does this is their own personal choice. Between the Iron, Silicon, Insolubles, and Acidity results, I think I made the right choice to get rid of the factory fill. The next question is whether I should do another replacement in 15,000 miles (at 20K odometer); or do I just roll the dice on 60K miles. Being somewhat obsessive on maintenance, I am tending to think I will do a fluid replacement at the 20K mark. Depending on what the analysis results are at the 20K mark will determine my next course of action.

 

I've been collecting PdMA samples in the files section of Yahoogroup, "toyota-prius-sat2" in the 'files' section labled "transaxle oil tests."

I would like to offer some thoughts based upon the Type WS and Type T-IV samples. Just opinions, feel free to forward them to Blackstone:

• Al(17), Si(140) - way too high, especially the 140 ppm Si. This strongly suggests dirt/grit in the oil, which this early change probably removed the greater portion. We have seen high Si levels of 227, 258, 153 in NHW11 and one NHW20 sample after 53-61k miles.
• Fe(58), Cu(7) - suggests wear material from what ever is in the oil. The early change helped but some of the Fe levels seen: 116, 206 but others have been significantly lower. Cu levels are OK, certainly we've seen worse.
• Insolubles - if this is fine particles, I would want to see a particle distribution test. Check if Blackstone still has enough sample to measure the distribution of different sized particles. PdMA charges extra for this test. Do you remember if the oil was opaque when it came out?

To see some of the results:
http://hiwaay.net/~bzwilson/prius/pri_T_cold.html#TRANSAXLE

Alternatively, go to the "toyota-prius-sat2" and check the collected samples.

I think you made the right decision and would like to suggest sending me a PM with an address. I'll send you a sample bottle that you can use to draw a sample from the fill port. If you can draw a sample at say 1k miles, we can determine how much was carried forward in the change.

Bob Wilson

 

It was a mildly translucent (but nowhere opaque) red color.

That is an interesting idea (an intermediate test to see where things stand after the first fluid replacement). It could either argue for a sooner 2nd fluid replacement (like say in another 5,000 miles); or, for keeping to the planned replacement in 15,000 miles. Should I sample again at 1,000 miles, or would 2,000 be a better metric (for more opportunity to sample for break-in metal bits)?

I don't want to sound too pedantic, and my apologies in advance if I seem to be going too deep into the weeds, but this is tweaking my curiosity about the car and how things are breaking in.

 

It is an area I have a current interest in exploring. My literature suggests that the fine, 3-7 micron, particles are the ones that lead to increased drag by bridging the oil film. Some of the early Prius fleet studies make a lot more sense if an early accumulation of 3-7 micron particles are being created.

Curiosity is good and led to my transaxle oil studies. My first change was a real eye opener but it has taken time to figure out a better testing protocol. So let me explain the semi-log sampling scale:

• 1 k - gives a true baseline including the dilution from old oil
• 2 k - gives initial wear pattern
• 5 k - confirms wear pattern
• 10 k - check viscosity loss, 15% means time to change
• 20 k - Type T-IV (NHW11) oil viscosity often down 15%, change it
• 50 k - Type WS (NHW20) oil viscosity check for 15% decrease

These are the goals but schedules often mean in real life, different intervals are used. Right now I have a 1.5k and 3.5k sample test. I'm at 8.5k miles so I'm going to 10k before my next sample and change.

My next change will include: 1) top plug sample, 2) bottom plug sample, and 3) mid-stream (proper) sample. I will also keep a sample for other experiments. I'll also wipe and clean the pan and drain the area under the differential.

Bob Wilson

 

You have definitely put a lot of thought into a monitoring plan. In my particular circumstance (having gone 5K on the factory fill before fluid replacement), I think that I will sample in 2K (7,000 odometer reading). Depending on what comes back in the analysis, another sample may be taken in 3K (10,000 odometer reading).

Thanks again for the feedback.

 

I replaced my transaxle fluid at 9562 miles and sent a sample to PdMA. My results are posted in the files at "toyota-prius-sat2".

Just for comparison to yours, they flagged

Fe = 64ppm
Al = 30ppm

they did not flag Si but,

Si = 147ppm

So, my results compare pretty closely for Fe and Si, mine was higher for Al.

I'm planning on taking a sample (but not replacing) in another 10k (10k on new ATF, 20k on the car). I just turned 14k this week.

 

Out of curiosity, was acidity tested? I was surprised at the acidity level of my oil. I'm going to be real interested in changes from the 5K mile results vs. the 7K mile sample when I take it. While oil testing may seem to be excessively pedantic (especially taking a second sample at 7K miles), it (at least for me) is a window into how my car is breaking in.

 

Re: Particles in Transaxle Oil

I just got around to checking my gas receipts for the fillup after the transaxle fluid was replaced - I gained 2 mpgs. Now the gain could be explained by the ICE continuing to break-in; but, I am intrigued about possible drag from particles in the transaxle fluid. Could you elaborate on what you have learned about drag and the early accumulation of 3-7 micron particles?

 

No, they did not test for acidity or TBN.

But, my understanding is that the acids that build up in motor oil are a result of blow-by from the combustion process. I am not sure how this would apply to the transaxle. I think that for the transaxle, you would want to watch for contamination from wear and viscosity breakdown which would affect the lubrication properties of the ATF.

I still have a 8oz. sample that I took in addition to the one I sent to PdMA.

I'm attaching the PDF file which has my sample from 9562 miles plus a VOA for comparison.

 

Re: Particles in Transaxle Oil

My first clue came from articles:
http://www.practicingoilanalysis.com/article_detail.asp?articleid=781&relatedbookgroup=OilAnalysis
http://www.practicingoilanalysis.com/article_detail.asp?articleid=401&relatedbookgroup=PowerGen

My investigation of transaxle lubrication has been going on for two years:
http://hiwaay.net/~bzwilson/prius/pri_T_cold.html
http://hiwaay.net/~bzwilson/prius/pri_tt.html
http://hiwaay.net/~bzwilson/prius/pri_toil.html

It was inspired by two key reports:
ORNL/TM-2004/247 - UT Battelle Report on transaxle performance
INL/CON-05-00964 - "Hybrid Electric Vehicle Testing"

In the "INL/CON-05-00964" report, the page titled "Fleet Testing Monthly MPG" shows that both Prius started out with higher mileage that decreased and never recovered later. One hypothesis is some combination of problems, not yet diagnosed, are causing Prius performance to decrease in service.

What "ORNL/TM-2004/247" showed is the lubricant can make a significant impact on vehicle drag. This report shows the temperature correlation, which maps to viscosity. However, they didn't look at particulates in the oil.

This is where some of the transaxle oil analysis are eye opening. The particle loads, especially in the 3-7 micro range, are impressive in a bad way. Yet there is no mechanism except for oil change, to get rid of these particles. So I've become more interested in investigating this area.

Bob Wilson

 

I have to admit that I am learning new things about the Prius. I certainly would not have expected to have an acidic sample after only 5,000 miles on a 'lifetime' fluid. Which makes me very curious about the results of my next sample at 7,000 miles on the odometer.

 

Re: Particles in Transaxle Oil

Eye opening seems to be something of an understatement.... I am waiting with great anticipation to learn what my next sample results will show. Interesting, interesting, interesting.

 

There is a mechanism related to aeration for 'dieseling' the transaxle oil. Apparently small bubbles can be compressed between gear teeth and the high pressure, gas compression heat ignites the small bubbles. But there is no mechanism for exhausting the products and in particular, small particulate carbon . . . diesel 'smoke.' The other by-products accumulate and over time, the acid level increases.

Near as I can tell, the differential gears are half immersed in transaxle oil. Furthermore, oil is sprayed about and obviously the film will get between the various gear teeth. It is another area I'm curious about and have started looking at by getting acid/base testing on selected samples.

Bob Wilson

 

Interesting concept. The pressure of the gear teeth on the oil molecules could in fact create a 'dieseling' scenario.

I definitely will get the TAN test done again at the 7,000 odometer reading. Stay tuned. Only 1,000 miles to go until 7,000.

 

I have a 30K sample to be tested, is the "standard" Blackstone test sufficient?

Thanks...Dan.

 

Normally we like to see the viscosity at 40C, 100C and the viscosity index. These three numbers give us a good idea of oils ability to lubricate the transaxle. I have been using PdMA because with the additional oil viscosity test it costs only $20.

It is important to note age of vehicle and total miles as well as the 30k miles oil service upon change.

Thanks,
Bob Wilson

 

Any recommendation for where to have it tested? What do I ask for?
(I'm on the west coast, if that matters)

 

I use PdMA but there are others that can do a good job. Nora corporation comes to mind. Just contact them first and get the price of a basic oil test and 40C/100C viscosity and oil index.

GOOD LUCK!
Bob Wilson

 

Very interesting thread and data from bwilson4web.

Does anyone know how the transaxle oil breakdown changes with frequency of cold starts versus continous freeway driving?

Does continous freeway driving (presumably at an elevated temperature) break down the transaxle oil lubrication properties faster than more frequent temperature changes in the oil with short frequent trips?

I'm at 60K miles and my commute is 100 miles roundtrip. From data presented it would seem that doing a transaxle oil change soon would be a good idea. However, its an expensive service item.

Thanks
Dave