CVT UOA 2004 Prius 65553 miles

[attachmentid=9778]I did a used oil analysis (UOA) on the CVT fluid. I have read that some have determined that a change at 50000 miles on the transmission fluid is a good idea. Based on this data from Dyson Analysis an even shorter interval is a good idea in my opinion, even though the recommended interval is "lifetime". I will also attach it in an excel file for readability.

Dyson Analysis
6/30/2007
2004 Prius CVT Fluid
Toyota WS Trans Fluid
Oil Miles ___ 65553
Trans Mi___ 65553
Iron______ 318
Copper____ 25
Tin_______ 0
Lead______ 0
Chrom____ 4
Nickel_____ 10
Alum_____ 77
Titan______ 0
Silver_____ 0
Calcium___ 134
Magnes___ 5
Zinc______ 15
Phosp_____ 210
Barium____ 24
Molyb_____ 0
Antim_____ 0
Silicon____ 179
Sodium___ 5
Boron_____ 58
Potass____ 0
Vanadium_ 0
Visc40C___ 21.1
Visc100C__ 4.8
TAN______ 0.85
Flash_____ 325
Oxida_____ 43
Nitrat_____ 5
H20(KFppm) 311
TBN______ 10.2
Fuel______ NT
Soot______ 0
Visc Index_ 155
Sulfate____ 33

 

<div class='quotetop'>QUOTE(efusco @ Jul 16 2007, 10:05 AM) [snapback]479558[/snapback]</div>

The levels that are of particular concern are Fe, Al, and Si. Often Si is from dirt, but it can also be from seals and such leaching Si into the fluid. Typically a good analysis would have Fe and Al levels about 1/5 to 1/3 of the levels in my report. Dyson Analysis tends to get higher wear numbers than many other labs and supposedly uses more sophisticated techniques so it is difficult to make comparisons from one lab to another. For reference, an engine oil sample at 5000 miles typically has Fe=5 ppm and Al=3 ppm, if you multiply by 13 to get 65000 miles you would have Fe= 65 ppm and Al = 39 ppm. I don't have access to "normal" values for a Prius, but the fluid change is something a decent mechanic could do in 15 min and the fluid costs about $40 so it could be done for $75 at an independent shop if you bring 4 qts of fluid from the Toyota dealer. Not a bad preventive maintenance item if you plan on keeping the car. I think jayman has mentioned that an early change of the Transmission fluid at maybe 10k and then shorter changes of maybe 30k would be prudent. Based on my uoa and the other analysis above I would agree. I plan to take a sample at 15k on the current change and get it analyzed and will post those results (probably next spring because I only drive about 20k per year).

Note that many of those components are additives and a TAN of less than 1.0 is good, but the wear metals (Fe, Al, Cr, Ni, Sn) are the main thing to pay attention to as well as the viscosity. If you compare the viscosity of the virgin fluid to the fluid with 61k on it you will see that it thinned a little, but not excessively in my opinion.