Just wanted to report a good high mileage transmission fluid change, I have a 2001 3.0i x5 with 193k miles, Never had a fluid change as far as im aware, the Fluid that came out was Black like oil, I bought the Castrol Dex6 for my GM tranny thanks to a member on here for clarifying the correct fluid. Reason i felt i needed to do the oil change was because i was expierencing a hard shift from first to second on harder acceleration, if i drove normally which i usually do it would always shift smooth and precisely in every gear as if nothing was wrong, so i wanted to see if new fluid would help with that jerk into second. Well the first drain and fill made it less noticeable, but still there if i pushed the car harder from a stop, well i waited a couples weeks in between the change so that i wouldn't shock the transmission with new fluid, so today i just did the second drain and fill and what a difference! It literally feels like new, you don't feel any shifts at all and it even feels peppier, the shifts are smooth as butter and quick, it also completely got rid of my hard shifting between first and second which was the main goal of this and to have that peace of mind. That said i would definitely recommend draining and filling your transmission at least twice, it could help you save your transmission. The real test is long term but i have no doubts. Have a great weekend everyone!