Originally Posted by Chriztofor
You don't HAVE to use BMW coolant. It is not magical coolant. The most important part is to make sure you follow the venting procedure, which is a simple process. Do a search on here. I believe eninty has a DIY on here. How I do it is to remove the undercover, remove one of the blue screws to the radiator, refill, vent, refill, and vent (not a typo; when you vent you will need to add more coolant. Eninty has you remove the waterpump hose(s) which can be a PITA. It is the correct thing to do, but I skip that.
You should use G-48, which is what BMW coolant is. And there doesn't seem to be any handy sources of G-48 that are significantly cheaper than the dealer, so you might as well use dealer coolant unless it's really hard to get.
G-48 has plastic compatibility specs which are different from some otherwise very similar coolants.