Breakdown: Why cold weather can affect cars fuel economy

Gas Gage of Labeled for Reuse Graphic
Gas Gage of Labeled for Reuse Graphic(WMC Action News 5)
Published: Mar. 7, 2019 at 9:12 AM CST
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MEMPHIS, TN (WMC) - When driving your car during the winter months, you might notice that the gas gauge is going down faster than during the summer. Did you know that the cold weather actually affects the fuel economy of your car?

In this episode of The Breakdown, we explain the reason why cars will obtain lower miles-per-gallon during the winter compared to the spring and summer time.

According to the U.S. Department of Energy, fuel economy tests show, in short-trip city driving, a conventional gasoline car’s gas mileage is about 12 percent lower at 20 degrees Fahrenheit than it would be at 77 degrees Fahrenheit. It can drop as much as 22 percent for very short trips, around 3 to 4 miles.

The effect on hybrid cars is worse; their fuel economy can drop about 31 percent to 34 percent under the cold and wintry conditions.

Why is this fuel economy lower? Well, the cold weather will affect your vehicle in more ways than you might expect.

Engine and transmission friction will increase in colder temperatures due to cold engine oil and other drive-line fluids.

This means it will take longer for your engine to reach its most fuel-efficient temperature. This will affect shorter trips more, since your car spends more time in less-than-optimal temperatures.

Heated seats, window defrosters, and heater fans use additional power, causing lower fuel efficiency.

Warming up your vehicle before you start will lower your fuel economy; idling gets you 0 miles per gallon, naturally.

Colder air is denser, increasing aerodynamic drag on your vehicle, especially at highway speeds.

In a previous breakdown, we talked about how tire pressure decreases in colder temperatures, thus increasing rolling resistance.

Winter grades of gasoline can have slightly less energy per gallon than summer blends.

Finally, your battery performance will decrease in cold weather, making it hard for your alternator to keep your battery charged. This will also affect the performance of the regenerative braking system on hybrids.

All this means if you notice that gauge dropping fast, or your MPG Range estimate on your car lower than the summer, just know that the cold weather makes your machine work harder, lowering its efficiency.

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