I didn't realize that BMW recommends nitrate/phosphate-free coolant. Last night, I was just checking out my 2010 X5 for a road trip this weekend (checked the tires, water, etc.) and saw that the coolant level was low. I had a jug of coolant in the garage and just filled it up with 50/50 coolant and water (filtered via reverse osmosis). I didn't put much coolant in though because the reservoir wasn't very low.

It's not a big deal, right? Or, am I just being paranoid because it wasn't one of the listed non-OEM coolants allowed by BMW, but one I bought from Autozone a few years ago.