Summertime Fuel Efficiency

In these dog days of summer, getting into a hot car can feel about the same as stepping into a sauna. With this July being the warmest on record for Lafayette (as if you couldn't feel that lovely oven air every afternoon), it's important to stay cool for your safety.

It's possible to stay cool in your car without sacrificing your fuel efficiency. In some ways, the summertime can actually increase your fuel economy: your engine warms up to an efficient temperature faster, summer grades of gasoline can have slightly more energy and warm air causes less aerodynamic drag than cold air.

The biggest culprit to reducing your fuel efficiency is your good old air conditioner. And second place goes to windows rolled down. According to the Department of Energy, under very hot conditions, air conditioners use can reduce a conventional vehicle's fuel economy by more than 25%. The effect on hybrids, plug-in hybrids and electric vehicles can be even larger.
Rolling the windows down increases drag, or wind resistance, requiring that your vehicle use more energy to push through the air, moreso at higher speeds.

You probably don't want to use a big portion of your gas to simply cool off inside, and there are easy ways to stay comfortable and efficient:
  • Park in the shade or use a windshield sunshade so that the cabin doesn't get as hot.
  • Roll the windows down at lower speeds in the city and use the AC on the highway.
  • Don't use the AC more than needed or set the temperature lower than needed. Once you're comfortable, turn it down a little.
  • Drive with the windows open for a short time before using the AC. Letting hot air out of the cabin first will put less demand on the AC and help your vehicle cool faster.
  • Don't idle with the AC running before driving. Turn the AC on after you begin to drive or after airing out the cabin briefly. Most AC systems will cool the vehicle faster while driving.
  • Read your owner's manual. Most manuals explain how the AC system controls work and how to best use and maintain the AC system.
  • For plug-in hybrids and electric vehicles, pre-cooling the cabin while plugged into the charger can extend your vehicle's range. Also, using a warmer temperature setting for the AC will use less battery power.
(Tips courtesy of

Although parking in shade is the best, it's not always possible. Many parking lots don't even have trees, and those that do have limited shade parking. And funny how those are the spots taken first.

So, sunshades are one of my favorite ways to keep cool. They don't cost much, they can show off your style, and they work WONDERS on a hot day. Auto Anything reports that sunshades can reduce the temperature inside your car up to 40 degrees. And whether it's natural shade or a sunshade, if your car is cooler inside to begin with, your air conditioner doesn't have to work as hard, minimizing its impact on your gas tank.

The shades range from the foil accordion-fold style to the pop-up style. Some are reversible to work in the wintertime, keeping the heat IN. (Can we all please dream of having this problem? #TooMuchSummer) The shades also protect your vinyl and any belongings inside, and keep your metal seat belt buckles from getting too hot. All without requiring gas or electricity.

Other tips from CNET for staying cool:
  • Use your bottom air vents. Since heat rises, the best method is to push the hot air out from the bottom to cool the vehicle as quick as possible, by helping the stale hot air escape through the open windows. Once the hot air is pushed out, switch to the upper vents to stay cool while driving.
  • Switch your A/C settings. Set the intake on "fresh air" and not "recirculation" when you first enter your vehicle. Recirculation draws in the interior air and typically works best once the vehicle has reached its desired temperature.
And no matter where you park, for how long or whether you use a sunshade, never leave children or pets inside the car. Even with taking these measures, cars can still get too hot for safety very quickly.

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