Absolutely not gonna happen. The only kind of fluid you do not want to even consider is a DOT 5 silicone fluid because it doesn't mix with the standard glycol-based fluids. As a practical matter, you will not find anything with specs lower than DOT 3 and even DOT 3 fluids are adequate, if not optimal, for use in your BMW's system. The vast majority of us use DOT 4 fluids, the only differences being whether it is a synthetic fluid. The better synthetics have the highest boiling points, with race fluids being the highest. For street use, you would virtually never have a use for anything more exotic than good old Castrol LMA, which is cheap and available everywhere. I snagged a deal on liter tins of ATE Super Blue a few years ago and I don't mind alternating it with either LMA or the ATE Typ 200 (identical to Super Blue except it's golden yellow). The different color makes it very easy to see when you've flushed the old fluid out during your annual fluid change.