Originally Posted by tempestv8

Since that date of my post, the X3's auto gearbox is still shifting smoothly and without any issues after the fluid change. So all I can say is that draining out the transmission's old fluid and putting in the Dexron 6 hasn't had any adverse effects. The condition of the original fluid in the gearbox was simply shocking - it looked much like used engine oil, although it did not smell burnt.

I'm just glad that at least half of that dark fluid is out and there's some fresh fluid in the gearbox. It's not possible to get it all out without a flushing machine.

All I can say is that no fluid lasts forever, so forget about this "lifetime" concept and treat the fluid as some kind of "extended life" fluid - eventually heat and friction will take its toll on the fluid and break it down, so don't procrastinate - just get it changed. And buy fluid from your BMW dealer - just to be on the safe side.