I use the BMW coolant although I don't think there is much of a difference between Bmw and generic fluid. Some manufacturers add special chemicals to their fluids so you only use their fluids ie:chevrolet diff fluid, their diff's won't work properly unless you use their fluid, maybe the same for BMW, I'd rather be safe than sorry, spending a little more on fluids makes more sense for me than taking the risk of having to spend $3000 on new cooling system and head work.