I didn't think it would work in such cold temps but it did. Keeping the climate on 73F in comfort mode, with the fan on low, caused the engine to come on once in a 40 minute drive. The engine comes on once right when you start the car and that's it. This means that the coolant can reach it's required 150F approx. even in the extreme cold. Not sure if it would work in zero or negative degree situations....