Personally, I would stick with the blue BMW brand. It's not much more expensive than aftermarket brands and has been proven to be safe for all of the metals in the engine and radiator. Dex-Cool has also been known to turn to a thick, gooey mud if it gets contaminated. It's perhaps the worse anti-freeze for this problem. (Google "Dex Cool Problem").
I often wonder if it's necessary for OEMs to create their own coolant and tell owners to use no other type, but it's not too expensive just to follow their advice. My garage now has specific coolants for BMW, GM, Honda, and John Deere. In the particular case of John Deere, I know a JD mechanic who used to replace lots of water pumps due to cavitation problems, but those problems have completely gone away with the use of the JD-specific coolant. While I've never heard of cavitation problems in automobile engines, it shows how original manufacturers can optimize fluids for their application.
Last edited by Blacklane; 05-03-2014 at 08:20 AM.