Cold weather and winter driving conditions can reduce your fuel economy significantly.
Fuel economy tests show that, in short-trip city driving, a conventional gasoline car’s gas mileage is about 12% lower at 20°F than it would be at 77°F. It can drop as much as 22% for very short trips (3 to 4 miles).
The effect on hybrids is worse. Their fuel economy can drop about 31% to 34% under these conditions.
Why is winter fuel economy lower?
Cold weather affects your vehicle in more ways than you might expect:
- Engine and transmission friction increases in cold temperatures due to cold engine oil and other drive-line fluids.
- It takes longer for your engine to reach its most fuel-efficient temperature. This affects shorter trips more, since your car spends more of your trip at less-than-optimal temperatures.
- Heated seats, window defrosters, and heater fans use additional power.
- Warming up your vehicle before you start your trip lowers your fuel economy—idling gets 0 miles per gallon.
- Colder air is denser, increasing aerodynamic drag on your vehicle, especially at highway speeds.
- Tire pressure decreases in colder temperatures, increasing rolling resistance.
- Winter grades of gasoline can have slightly less energy per gallon than summer blends.
- Battery performance decreases in cold weather, making it harder for your alternator to keep your battery charged. This also affects the performance of the regenerative braking system on hybrids.