Why Your Gas Mileage Gets Worse in Winter & What to Do About It

poor gas mileage in winter

Cold weather can take a real toll on your gas mileage.  As I pointed out in an earlier post about winter gas prices, gas companies sell a different fuel blend in the winter, which produces less power.  That’s not the whole story, though.  There are a number of other reasons why you have to gas up more once it gets cold out.

The Impact of Frigid Temperature on Your Auto

The first is that your engine has to work harder in the cold.  First of all, the oil that lubricates your engine gets thicker when it’s cold, which means there’s more friction on the moving engine parts.  You also probably use more electric accessories during the winter.  Think of your heating fan, lights, defrosters, windshield wipers, and all the other parts that draw on the battery.  You run a lot of these more often in the winter.  That drains the battery (which already drains more easily in cold conditions) and means the alternator has to work harder.

The grip of your tires also contributes to your fuel use.  As tires roll, they actually flex a bit to make a contact patch with the road.  That helps you get more grip.  Rubber gets stiffer in the cold, so it doesn’t flex as well.  That means they’ll have a smaller contact patch on the road and less grip.  That means you have to use more power just to get going.  If your wheels slip, then you’re really wasting power.  The engine’s pushing but you aren’t getting anywhere.

Added weight and poor aerodynamics can also mean that it takes more power and more gas to get where you’re going.  First of all, cold air is denser, so it’s harder to cut through the air.  It doesn’t help if you leave a pile of snow on top of your roof when you pull out of the drive way.  The snow adds extra weight too, which doesn’t help, but that might not be the only extra weight.  You might have a shovel and other cold weather gear in your trunk, which I won’t blame you for.

What Can I do?

Probably the best thing you can do for your car in the winter is to keep it in a garage, if you can.  That will keep it warmer which makes warming up the engine easier.  It also makes the cabin warm up quicker, which means you won’t drain the battery as much running the heating fan, defroster or heated seats.  A warmer battery will also work better, so it’s pretty much a win all around.

Another tip to help you avoid many of these problems is allowing the engine to warm up.  That doesn’t mean letting it idle for a long time, though.  When you car is idling, you get 0 miles per gallon, because you’re burning gas and not going anywhere.  A minute or two of idling should be enough.  Then, drive gently.  Since a warm engine runs more efficiently, you’ll want to lump your trips together.  If you’re running errands, you can also start with the one farthest way, to give your engine the most thorough warm up, and then work your way back towards home.

You should also look into getting a good set of snow tires. Snow tires are more flexible and offer more grip, so they help you put the power the engine is producing to better use.  That will save you some of the expended gas.

 

Some people put sand bags in their trunks to weigh their cars down.  This can help a lot if you have a rear wheel drive car.  The extra weight helps your drive wheels dig in, in the snow.  If you have a front wheel drive car, though, the engine puts plenty of weight over your drive wheels.

If you have accessories on the outside of your car that you aren’t using, like a bike rack, take them off to remove weight and improve your aerodynamics.

Even if you follow all of these tips, you’ll probably see some reduction in fuel economy in the winter.  There’s nothing you can do to make winter gas burn better or to reduce the density of cold air.  That being said, following these tips can at least lessen the impact and save you a bit of gas and money.

Written by Dan Smolinsky.

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