[horizon]

There are a lot of inaccuracies here. This is out of the BMW operating fluids TSB. It says:
"The cooling system of BMW cars must only be filled with reputable brand name ethylene glycol long-term antifreeze
having corrosion inhibitors that are compatible with aluminum radiators.
Coolants must fulfill four basic requirements.
— Guarantee sufficient cooling.
— Protect various metals (gray cast iron, steel, aluminum alloys, brass, copper and solder) against corrosion.
— Prevent excessive silicate gel precipitation, which may cause clogging of the cooling system.
— Guarantee operation of cooling system in winter (prevent freezing of coolant) and in summer by boosting the boiling
point."

This would mean that any universal coolant would suffice as they are typically ethylene glycol long-term without silicates. This would be more than sufficient for topping off. If I were to flush, I'd use the BMW coolant.

[F32Fleet]

OEM. There's no savings to be had by going with something else.

[Surly73]

A couple of points I've mentioned before.

1/ OEM coolant is G-48. G-05 is close but not quite the same. IN a BASF spec sheet (which has since been taken offline) one of the major factors in G-48 is "plastic compatibility". Considering the amount of plastic in the system, this might be important. Nothing's going to explode immediately, but you might have a weird probably 4 years from now and never put the two together.

2/ If you can't find G-48, you can use G-05 in a pinch but G-48 would be better

3/ Waterwetter and BMW OE coolant are incompatible and the Waterwetter will turn into a brown greasy substance after a couple of months. It will coat the engine internals inside the block with the stuff and generally make a mess. Just don't do it.

[gde061]

I found the G-48 data sheet online here. I know this is an old post, but since search keeps coming up with it I figure it's worth updating.

Of note, the G-48 has silicates (other threads mention that). As pointed out above by [user]horizon[/user], most green "universal" coolant specifically does not. Silicates are called "liquid glass" and are used in sealing concrete and such. So more than likely their presence or absence will effect plastics and rubber o-rings differently (seems like it should harden them - which probably aids longevity but makes the hoses harder to pull off).

[slinkygn]

Well, I wasn't about to bump an ancient post, but since somebody else did it for me...

Just wanted to note that I just bought some Zerex G-48 at O'Reilly (in the US), and I've been buying it there for quite a while too - pretty sure even as far back as when somebody posted that "you can't buy it retail" earlier. Certainly isn't the cheapest coolant they stock, and no idea what dealers charge for coolant, so for all I know I could be losing money on the deal... but it's certainly available.

[JasW]

I still have 2/3rds of a gallon of OEM coolant that I bought 7 years ago for my former 335i. It's been sitting in my (usually hot) garage since. Anyone think I should have a concern about using it?