[imyy4u]

Hello, I have an F90 M5C (2020) and I live in Chicago. Right now our high temps have been around -5 to -1 F. Really fucking cold.

And when I first start my car, I get a warning: engine coolant low. I let the car run 10-20 seconds, turn off, turn on, and I'm fine.

So...what's going on? Do I have just barely enough coolant? Is it the temp? And how can I manually check my coolant level?

[GTTC]

Fluids contracts under the influence of a low energy system (cold). In your case is very cold. Coolant should be 50/50 distilled water and whatever antifreeze you have (I assume HT12). This mix should lower the freezing point (some say -32F but this is almost perfecr mix and new). Expect some low coolant indication until the car warms up.
To manualy check just open the cap of the driver’s side of the engine (bigger cap) and shine a light. Should see a yellow tab that says Max/Min and you should be right in the middle.
I suggest to let the car warm up to normal temp and let it rest for a bit. Given your cold temps it should’t take too long and remove the cap (just make sure is not HOT but warm. HOT will BURN you). The overall temp should be warm enough to give you a good level.
If you didn’t have an issue before cold weather I think it should be ok, but since I’m OCD it would drive me crazy.

Hope it helps, and stay warm!