I'm sure one question you're about to ask is "what type of coolant should I use?" BMW has issued a 1991 technical bulletin, 17 01 88(1743), which details problems with what is known as silicate gel precipitation in engines. This is the 'green goo' (yes, it actually says that in the BMW Tech bulletin - gotta love those German translators) that results as a consequence of an antifreeze over-concentration in the coolant, combined with hard water, and the phospates commonly used in many antifreezes. BMW factory antifreeze has been formulated to prevent this problem of silicate drop-out without any coolant performance loss. This antifreeze contains no nitrites and no phosphates. The part number for a one gallon container is 88-88-6-900-316, and it costs about $13.00 per gallon. Although I am always eager to find alternatives to BMW factory products, I would stick with the factory coolant for now.
