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How to Save Fuel in Hot Weather

by on Jun.19, 2014

You can save fuel driving in summer - if your're careful. Photo courtesy: DenverExpressCare.

It was a long, cold winter for much of the U.S., and if you live in one of those Snowbelt states you might have noticed that your fuel bills rose whenever the mercury sank, your car working longer and harder to get both the engine and passenger compartment up to temperature. The good news is that hot weather actually can reduce your fuel consumption – at least if you follow some basic tips.

While your engine warms up faster – requiring less fuel – you need to think about ways to keep the passenger compartment cool without putting the air conditioning on at full blast, cautions the Department of Energy (DoE) and other automotive experts.

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“Under very hot conditions, AC can reduce a conventional vehicle’s fuel economy by more than 25%,” notes new guidelines posted on Fueleconomy.gov. And the impact of running your air conditioning in a hybrid, plug-in or battery-electric vehicle “can be even larger on a percentage basis,” it notes.

In the days before AC became pretty much standard across the board, you’d likely keep your windows open while driving on a hot day. Surprisingly, that isn’t a good way to cut down on the cost of running your car’s AC, expects note. Today’s vehicles are designed to maximize aerodynamics – or to put it another way, to minimize drag. And while this might not matter when you’re cruising around town at low speeds, wind resistance increases exponentially when you get on the highway, and the added drag of leaving your window open is likely to use more fuel than running your AC.

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That said, the DoE says opening your windows to let out the excess heat when you start your car on a hot day is more efficient than trying to cool down what is essentially a greenhouse. Start the AC on after you get the engine running and have aired out the cabin.  Air conditioning usually is more effective and efficient when you are moving.

Other recommendations from the DoE and other sources:

  • Get a summer service check to make sure your car is in tune. It uses less fuel when it’s running efficiently;
  • A tune-up doesn’t apply only to the engine. Make sure the AC system is checked and has the proper level of coolant to run most efficiently. Also make sure your radiator has enough antifreeze which, in summer, helps prevent boilover;
  • When you park, look for a spot in the shade, or get a sunshade that can reflect or block the sun’s rays.

If you own a plug-based vehicle, such as a Nissan Leaf or Chevrolet Volt, chances are you can pre-cool the cabin (and pre-heat it during the winter) while it’s still connected to its charger. That not only means it will be pleasant to climb into but that you’ll also maximize range.

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“Also, using a warmer temperature setting for the AC will use less battery power,” notes the Fueleconomy.gov page.

Whatever time of year, the experts suggest driving at or under the speed limit can save as much as 33% of your fuel. Coasting to a stop, rather than slamming the brakes, can reduce your bills – while it also pays off to start out smoothly, rather than making jackrabbit starts when the light turns green.

Your tires can have a substantial impact on mileage – by some estimates, as much as 10% of your fuel economy. The AAA recommends regularly checking your tire to ensure their at the pressure recommended by the manufacturer or tire maker. It’s best to check in the morning, before temperatures rise and pressures increase. Road friction also increases pressure, so check before you begin your commute or start running errands.

(Summer brings the “100 deadliest days” for teen drivers. Click Here for the story.)

And, of course, it pays to compare fuel prices. Warehouse clubs and grocery stores often have some of the best prices.

One folk tale that apparently doesn’t make a difference concerns the time of day when you fill up. Like other liquids, gasoline expands as it warms, but service stations normally store their fuel underground, where temperatures vary only slightly, so you won’t get more gas for your money in the cool of the morning.

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One Response to “How to Save Fuel in Hot Weather”

  1. Jorge says:

    While the story suggestions are fine and all the way for many U.S. drivers to save a huge amount of money on fuel is to get rid of the SUV they don’t need and buy a proper sized car.

    You would be amazed to hear the reasons why people buy SUVs when they don’t have any need for one. I often conduct opinion polls in car forums to see the mentality of people and it’s frightening sometimes as they haven’t a clue in the world.