The BMW stuff is always a good/safe choice but in the RepROM BMW says to use 'Nitrite-free long-life antifreeze and corrosion inhibitor', which describes most modern OAT antifreeze formulas. I would expect that any of the premium brands would be fine as long as they meet this spec (check their website for details) and are safe for all metals, and again these days they just about all are.
However... since you are only adding coolant vs. a refill and it's best not to mix different coolant technologies, unless you can confirm what you are adding is compatible with the existing formula it might be safest to stick with the BMW stuff if it is easily available. If not with a little research it should be easy to find a safe alternative, and Prestone and many others claim their latest formations provide universal compatibility.
Last edited by smiller; Jul 21st, 2013 at 3:41 pm.