I agree it's just a single data point. However, it really depends on who you ask. I had a conversation with a ZF technical rep a couple years ago related to the tiptronic trans in an Audi and a Porsche Boxster (same basic trans and they even share case parts). His recommendation was to change fluid, period. The only time changing atf at 80, 90, 100K miles was a problem was if the trans was already going bad, the detergents in fresh fluid might accelerate the failure. But if the trans was fine, there's no reason to not change fluid. At that time I had 75K on my Audi and he said go ahead and change it. In fact he said I'd be crazy to not change it if I wanted to keep the car for a while. Unfortunately I can't say if it would have affected long term reliability, the car got rear ended and totalled a few months later.

I guess the real solution is to not wait until 40 or 50K to change the fluid and filter, and just make it part of the 30K service intervals. Now if I could only convince my dealer to do this for the X5, I'd be a happy camper.

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'04 E53, 4.4 Sport
'97 E39 528i
'86 911 Carrera, track car
'96 BMW R1100R