What kind of anti-freeze would you recommend ?

BMW dealer has the approved antifreeze//coolant.

Hello, The prestone all makes all models coolant is compatible with everything, but do yourself a favor and drive the 30 miles. BMW knows exactly which materials the engine coolant contacts, the exact temperature, and the exact characteristics of the cooling system over time. Using their coolant ensures your very expensive engine stays protected. You can also order it online and have it shipped to your door.