You didn't ask for a fluid analysis, you asked for data that supports fluid lasting 100,000 miles. If that fluid has not caused a transmission failure by a significant margin beyond that 100,000 miles, then it seems a reasonable conclusion that the fluid has lasted. In the same day, we heard about another 40,000 mile transmission failure. That supports the MTBF hypothesis, ie that it is somewhat random.
Why bother with changing motor oil? Because it becomes contaminated by byproducts of combustion. If it was a case of it just getting dirty, we would just use better filters. Centrifugal spinner filters will clean the oil better than when it is originally supplied, and even fine cartridge oil filters (such as clean-up filters) will clean oil better than when it is new (yes, I have data). What we can't do is remove the chemicals related to combustion. For systems that require very clean fluid, it is common to use a dialysis-type off-board filter cart, to clean the fluid and put it back, because the fluid is fine, it just needs cleaning. In the case of an engine, the oil will itself cause a failure, due to the nature of the system. You can't compare engines and transmissions, they are completely different. I would compare a transmission more to a hydraulic system, where the fluid does lubricate, but also serves as an incompressible actuator and a heat conductor.
__________________
2007 X3 3.0si, 6 MT, Premium, White
Retired:
2008 535i, 6 MT, M Sport, Premium, Space Grey
2003 X5 3.0 Steptronic, Premium, Titanium Silver
2002 325xi 5 MT, Steel Grey
2004 Z4 3.0 Premium, Sport, SMG, Maldives Blue
|