Why do hybrids get less mpg during cold weather? While my fusion is at a red light on battery, the gas will cut in. Why?
All vehicles get less Miles per gallon in winter and batteries do not like cold.
How big of a drop?
If you are using the heater the engine will run more frequently to provide heat and maintain engine temperature for clean tailpipe emissions.
Be glad the engine comes on to supply heat in cold weather while you are stopped for a traffic signal. It takes fuel to produce heat.
The Citicar, a battery powered vehicle manufactured in the late 70s into the early 80s had an optional heater fueled by propane. The vapor produced caused the windshield to fog up. I would guess the cost of using propane to provide heat in the Citicar exceeds the cost of the extra fuel used in the hybrid Fusion to supply heat.
Winter formulated gasoline will get you fewer miles per gallon, and because of the high MPG of a hybrid, the difference will be more pronounced in MPG than on a normal car.