it's not ur coolant dude.... because it's so cold out, and the front of you car is open, u get a constant rush of cold air in ur engine bay, this makes ur motor cool down. If u want it to stay warm the whole time, u can do something as simple as placing a piece of cardboard infront of the radiator, so u don't get that freezing air under the hood. I have the same problems too, the only bad thing to this is that ur car kinda starts to overheat a little, thats why i took mine out, but in severe cold " like under 30 c " i'll put it back in. Truckers do this same thing, except they don't use cardboard, they have some special thing. Hope that helps