These are preliminary data but after 37,000 service miles, the Type WS viscosity numbers came out very good. The worst case projects to ~100,000 miles before changing is needed. The wear materials are well within limits and though the particle count seems high it was probably due to leaving out the capture magnet on the previous change. I'll post more details after I get it uploaded to SAT2 and then combine all data into a set of charts and graphs. If we can come up with a more practical way of achieving micro-filtration, we are looking at 100,000 mile service intervals or at my annual 20,000 miles per year, nearly 5 years . . . what a nice problem to have! Bob Wilson
You ought to offer week courses on Prius maintenance. I'd pay just to be facinated watching you strip the Prius and explain the technical aspects of its workings. Then there's always the southern hospitality for the evenings.
If I'm hearing you correctly, Bob, you're saying the once a year change on the Type WS advocated by some here is overkill?
I don't remember seeing anyone advocate an 'annual' transaxle oil change. But based upon what I'm seeing in the oil testing results: First change at 5,000-15,000 miles - This recommendation is based upon oil test results from three, well documented, first transaxle oil changes. If the transaxle oil hasn't been changed and the odometer reads over 15,000 miles, it is overdue. Both Type WS and Type T-IV. Second change at next 30,000-60,000 miles - this is based upon second oil change, test results that show some carry forward of the first oil and the continued effects of sealant debris accumulating in the oil. This is for Type WS with sooner for Type T-IV. No extended service for Type T-IV. Third and subsequent changes at next 90,000-100,000 miles - this is based upon third and later changes when we are seeing the sealant stabilizes and the early debris has been 'changed out.' This is for Type WS only. The transaxle oil study is not over. My wife's second, ZVW30 change is coming up in 5,000 miles, about January-February when it will have achieved 15,000 service miles. We'll have some other updates and testing to complete. Not the least is a detailed summary of my NHW11 transaxle oil change data. Bob Wilson
Let's say that someone doesn't change their transaxle oil before 15,000 miles. How is that "overdue"? In other words, what direct connection, if any, have you made between (a) the lack of such a service at the interval you state and (b) degraded transaxle performance or service life?
