Driving in the dead of winter is harsh on a vehicle, and many of you have undoubtedly noticed that your fuel economy suffers as temps dip. In practice, gas mileage drops approximately 10 percent when temps go from cozy (60-80 degrees Fahrenheit) to bitter cold (less than 32 degrees Fahrenheit). But why does the weather affect the gas mileage of your vehicle?

There are a number of reasons why below-freezing temps reduce the efficiency of a vehicle, but it all starts with the reformulated gasoline that flows from the pumps. Refiners modify gas to improve vehicle performance and reduce emissions. In the winter, refiners add components to gasoline to lower its freezing point. These additives are low in density and don't offer much in the way of energy. Basically, the additives take up space without contributing much to the combustion process. This means that the engine must gulp down more fuel to generate the same level of performance that it did when conditions were balmy.

In addition, cold temps cause lubricants to thicken, which increases resistance in the vehicle's engine, transmission and axles. But that's not all. Running accessories such as window defoggers and those priceless electric seat heaters sap energy from a car's electrical system, requiring the alternator to work overtime.

Then there's snow. The added resistance of driving through inches of the white stuff can take a toll on your vehicle's gas mileage. Finally, cold temps cause tires to lose psi. This, in turn, can lead to increased fuel consumption. Luckily, it's April. Meaning that summer is coming soon and your vehicle's fuel economy will likely improve. But, come next winter, when temps dip down below freezing, now you know why you're not going as far as you once did on a gallon of gas.

Note: To mark the 41st anniversary of Earth Day* this year on April 22nd, we're running a series called Countdown to Earth Day that we want to be very welcoming to new readers, both in topic and tone. We'll be returning to our Greenlings series for inspiration here, and if you have friends who you'd like to introduce to AutoblogGreen, perhaps these introductory posts and the coming "holiday" will be the spark to get their green car fire burning.

Image: nathanmac87 – C.C. License 2.0]

*Ironically, the apparent traditional gift for a 41st anniversary is land. Since land – earth – is something we can't easily create, perhaps this Earth Day we can give ourselves the gift of stewardship of the land.


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