BMW used to recommend driveline fluid changes every 30K miles. Probably if you followed that it would still work great. But that only works for the original owner who keeps one for a long time, which is not typical. These days it is more likely for the first owner to be a 3 year lease. The second owner then buys it as a CPO and keeps it 2-3 years. And the 3rd owner is buying a 6 year old car with 80K miles on it and the trans fluid has never been changed. I believe at that point you are better off leaving well enough alone. I suppose if changes had been made every 30-50K that would be another matter. The only car we currently have that we bought new is a 2003 Mazda that is my wifes car. I changed the trans fluid at 50K, 100K and 120K. The last one only because I was replacing the engine at the time so pretty much had to. I will change it again at 170K. I figure 50K is a pretty reasonable AT trans fluid change interval.

But in my X5 and 740i that I got at 90K miles a piece, I am not planning to touch either one. Let it ride and hope for the best. The trans may well fail, but more than likely if it does the reason will not be the fluid. And changing the fluid now could cause trouble. So I feel the odds are better in not changing it once you get that many miles and no changes have been done. I don't buy into the 100K mile service interval. I say you either do it every 30-50K miles from new, or don't do it at all.

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2003 4.6is - SOLD
2003 M5 Imola
2008 Mini Cooper S
2011 Mazda CX9