Thanks for the reps.

I definitely agree that trending wear metals will provide a lot of information (with sufficient number of samples) to see relative wear rates of metallic transmission components. That is the real value, seeing the component wear rates over time. It just won't tell you much about the fluid condition IMO unless the tests carried out can measure the various specifications for the fluid that are specific to each transmission fluid type. Given that the fluids are proprietary in many cases, determining what the spec is could be difficult (except for fluids like Dexron, which are more of an open standard). But I'll go over to BITOG to see what I can learn. Thanks.

Jeff

Edit: I see some discussion of particle counts, by both optical and automated mesh screen methods. Those can estimate an ISO cleanliness for the fluid. It would be interesting to try and get the cleanliness spec from ZF. I am familiar with the use of published ISO cleanliness specs for heavy equipment (has to come from the manufacturer of the equipment), but I suspect that ZF would be somewhat less forthcoming with the info. So, an estimated ISO cleanliness spec could be trended, but the pass/fail criteria would not be known.

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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