I'd be inclined to add some antigel as well. Better safe than sorry and all that.

We don't get the cold temps like you guys get(15ish is about as low as it gets) but I still add antigel. Doesn't cost much, not much hassle, and it would only take once having a fuel system full of butter to really make me wish I had treated it.

__________________
617 swapped Toyota Pickup, 22-24 MPG, 50k miles on swap