On my gf C-max Hydrid , in the Canadian winter, the ICE will start seconds after you turn the key on, even with a full charge. As it senses the cold, and that it need to be at operation temperature for later use. Versus now warmer, we can drive away in EV and the ICE will turn on when needed. Im sure the ECU will Command the ICE and E-heater to come on to heat up faster. For performance and comfort. Any car is harder on MPG in the winter. Exp, my BMW 550 does 16mpg in the Winter, and 19mpg in the summer. (combined mpg DD)