Type T oil --> 15,000 miles useful life
Hi folks,
Pending one more sample, we can pretty well nail the useful life of Type T-IV fuild in the NHW11, 01-03 Prius transaxle as 15,000 miles. Doug Schaefer's sample at 20,000 miles came in just over the 15% viscosity loss signalling the need to change the oil: http://hiwaay.net/~bzwilson/prius/pri_toil.html His wear metals came in at half of the next highest, 40,000 mile, sample. The straight-line between the 7,000 mile Amsoil and 20,000 mile Type T-IV intersects at 15,000 for both the 40C and 100C viscosity lines. I have one more test in progress that has another 5,000 miles to go. This last test is checking my vent plug modification so I won't have these results until later this year. But Doug's sample is enough to justify sharing these results. On my next change, I will be: 1) keeping the vent plug modification - avoids negative transaxle pressure and I need the test results before reporting success or failure. I may later add an oil desicant filter to further reduce potential water infusion after I get my test results. 2) installing nipple Fumoto plugs - one in the drain and one in the fill. These will be used for intermediate samples, oil level checking and a "batch" oil filter test. In the batch filter test, I will connect the nipples to a pump and filter and run it overnight. With pre and post filter samples, we'll see if this can make an appreciable reduction in oil particulates. It may also be a cleaner way to handle NHW20 filter installation. 3) Type W - has a starting viscosity range at the ending range of the type T. I suspect the Type T viscosity loss is mechanical, it is too thick for transaxle use. The Toyota SAE paper on the changes between the NHW11 and NHW20 cites use of an improved transaxle oil. I'm seeing a 50F increase in transaxle oil temperature suggesting a significant energy loss with Type T grade oil. I suspect Type W will improve performance and reduce wear in the NHW11 transaxle. I will be conducting an instrumented and documented test of the Type W after my Amsoil ATF test is complete. However, I understand others are already testing Type W. My expectation is the Type W should result in a noticable mileage improvement of at least 3 MPG but we need experimental confirmation. I was asked why worn out Type T doesn't have simular performance to new Type W? Certainly the hill rolling test showed new Amsoil ATF (Type T equivalent) out performed used Type T. The answer is the worn out Type T also carries a significant particulate load and viscosity loss is an indirect measure of 'film strength' for clean oil. Film strength is how much pressure must be exerted for two surfaces to push through oil to make contact. This is the 'slippery' factor of oil that along with viscosity, reduces friction. But oil filled with particulates basicly has solids that bridge the lubrication film. IT MAY BE POSSIBLE to filter used Type T and get simular film strength of Type W but that is pure speculation. So my recommendation for NHW11 owners (01-03 Prius) is: 1) change Type T transaxle oil every 15,000 miles until your transaxle warrantee has expired. Be sure your first change drops the pan and cleans out the gunk. As for use of Type W transaxle oil in an NHW11 (01-03 Prius), that experiment is in progress with one known sample and I will be joining the experiment later this year. IF you plan to test Type W in an NHW11 transaxle, please consider doing the following: 1) get a Fumoto drain valve - so you can take intermediate samples for testing. If you want to do the dual, nipple valve approach, fine by me. 2) drain, drop pan and clean - clean out all prior traces. If you have less than 20,000 miles on your current Type T oil, please save a sample in a clean container (dry polycarbonate or polyethelyne container) and contact me about getting a sample of the 'gunk'. Be sure to have tubing to drain the gallery to the rear. 3) perform early oil sample tests - we need samples at least every 15,000 miles of Type W oil in NHW11 transaxles. Basicly an annual oil sample and test with replacement of the Type W sample to keep the oil level constant. BTW, we have one Type W sample and a baseline from an NHW20, 04 Prius. The one sample indicates the oil is good for 60,000 miles in an NHW20. Until we get more samples from NHW20 transaxles, it is too soon to draw any conclusions. But the first sample looks pretty good! http://hiwaay.net/~bzwilson/prius/pri_T_cold.html One last point, I see no evidence of bulk, transaxle oil over heating. I have spent a significant amount of time at high speed on +100F highway travel and the oil has never reached 85C, the ICE thermostat temperature. This is with Amsoil ATF (Type T equivalent.) Limited hill climbing testing, ~950 ft / ~290 m, shows no evidence of transaxle oil heating. THERE MAYBE LOCAL HEATING in the bearings that I can not measure but I have not seen a bulk oil heat problem, yet. Bob Wilson |
Re: Type T oil --> 15,000 miles useful life
Bob,
Your work to date has delivered solid data for owners of the classic (US) Prius (NHW11). They should follow your Type T renewal suggestions at 15k mile intervals. I'm currently at 71k miles on my NHW20 (10k on the new Type WS ATF since the refill at 61k miles). My plan is to do an extra ATF refresh at 90K miles to give you one more sample point. My ETA to 90k is about 10 months so be patient. JeffD |
Re: Type T oil --> 15,000 miles useful life
Hi Jeffery,
Originally Posted by jdenenberg
. . .
I'm currently at 71k miles on my NHW20 (10k on the new Type WS ATF since the refill at 61k miles). My plan is to do an extra ATF refresh at 90K miles to give you one more sample point. My ETA to 90k is about 10 months so be patient. . . . 1) NHW11 samples from less than 30k miles 2) NHW20 samples from less than 60k miles (Please contact me if you have a sample from these groups.) We've also got some pioneers running Type WS in their NHW11s and early samples from their machines will be important. Fortunately, my current, Amsoil ATF (Type T), needs one more week to reach 13,000 miles. Anyone interested in contributing to the transaxle oil database can find it at: http://autos.groups.yahoo.com/group/...-sat2/database If you put in a sample, please identify your geographical area of operation. Bob Wilson |
Re: Type T oil --> 15,000 miles useful life
For some strange reason I think it would be nice if Bob bought a Honda Civic hybrid... We could use a guy like Bob!
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