Cold weather and winter driving conditions can significantly reduce fuel economy. Fuel economy tests show that, in city driving, a conventional gasoline car's gas mileage is roughly 15% lower at 20°F than it would be at 77°F. It can drop as much as 24% for short (3- to 4-mile) trips.
Cold weather effects can vary by vehicle model. However, expect conventional gasoline vehicles to suffer a 10% to 20% fuel economy loss in city driving and a 15% to 33% loss on short trips.
The effect on hybrids is typically greater - with fuel economy dropping about 30% to 34% under these conditions. For hybrids, fuel economy typically decreases by 20% to 40% in city driving and 25% to 45% on short trips.
For electric vehicles (EVs), fuel economy can drop roughly 39% in mixed city and highway driving, and range can drop by 41%. About two-thirds of the extra energy consumed is used to heat the cabin. When the cabin heater is not used, EV fuel economy is 8% lower at 20°F than at 75°F. Driving range is about 12% lower.
Why Winter Fuel Economy is Lower
Cold weather affects vehicles in more ways than one might expect:
- Engine and transmission friction increases in cold temperatures due to cold engine oil and other drive-line fluids.
- It takes longer for an engine to reach its most fuel-efficient temperature. This affects shorter trips more, since a vehicle spends more of a short trip at less-than-optimal temperatures.
- Heated seats, window defrosters, and heater fans use additional power.
- Warming up a vehicle before starting a trip lowers fuel economy—idling gets 0 miles per gallon.
- Colder air is denser, increasing aerodynamic drag on a 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 the alternator to keep the battery charged. This also affects the performance of the regenerative braking system on hybrids, plug-in hybrids, and electric vehicles.
In severe winter weather, mpg can drop even further.
- Icy or snow-covered roads decreases the tire's grip on the road, wasting energy.
- Safe driving speeds on slick roads can be much lower than normal, further reducing fuel economy, especially at speeds below 30 to 40 mph.
- Using four-wheel drive uses more fuel.
How to Improve Fuel Economy in Cold Weather
While it may not be possible to completely mitigate cold weather's effect on fuel economy, there are some simple steps to lessen the reduction in gas mileage:
- Park in a warmer place, such as a garage, to increase the initial temperature of the engine and cabin.
- Combine trips when possible to lessen the amount of driving with a cold engine.
- Minimize idling to warm up the car. Most manufacturers recommend driving off gently after about 30 seconds. The engine will warm up faster being driven, which will allow the heat to turn on sooner, decreasing fuel costs, and reducing emissions.
- Don't use seat warmers or defrosters more than necessary.
- Check tire pressure regularly.
- Use the type of oil recommended for cold weather driving by the vehicle manufacturer.
- Remove accessories that increase wind resistance, like roof racks, when not in use.
- For a plug-in hybrid or electric vehicle, preheating the cabin while plugged into the charger can extend the vehicle's range.
- Also for a plug-in hybrid or electric vehicle, using the seat warmers instead of the cabin heater can save energy and extend range.
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