The graph shows as speed increases gas consumed also increases. It gets really bad over 80kph and takes off from there. Keep in mind, they were testing an suv at 30 deg C. These results are only for this situation, it may vary with other cars.
Did they test this in that speed range? The treehugger study and the mythbusters study are the other two I have seen that have some research involved and those are the two that show ac off windows up is the best. I do appreciate this blog site letting us post comments though. Notify me of follow-up comments by email. Notify me of new posts by email.
Home About Advertise Contact. Filed Under: Aerodynamics , Car Maintenance. Comments b3n says. May 23, at am. John Waiveris says. William Wilgus says. July 9, at pm. Ayall Sagi says. October 4, at pm. And what size of Car? Does it make a difference? When you're driving around town at relatively low speeds, you'll use less gas by switching the air conditioner off and rolling down the windows [source: Arthur ]. It's more efficient to drive with the windows down at slow speeds as opposed to faster speeds because there's less aerodynamic drag when you're driving slower [source: Motavalli ].
As your speed increases, however, the amount of drag on the vehicle will also increase. But the drag doesn't increase in a linear fashion, it increases exponentially.
For example, when your vehicle is traveling at a speed of 70 miles per hour So even though the vehicle's speed is doubled, the drag is actually increased by four times. If you're searching for a good rule-of-thumb number for when it's best to open the windows and switch off the air conditioner, according to some experts, the cut-off should be around 40 miles per hour What's the reason?
Well, at low speeds your engine is producing less power , so it would have to work much harder to power accessories like the air compressor.
When the engine is operating at faster speeds, it's already producing ample power for both the engine and additional equipment [source: Austin ]. Although we've made the case for both windows down and air conditioning, some argue that the windows down option is still the better bet. Car and Driver did its own study and determined that you should switch off your air conditioner -- most of the time [source: Austin ]. However, the U.
Department of Energy recommends using both windows down and air conditioning when the conditions permit [source: U. Department of Energy ]. So, if you're conscious of going green to reduce fuel consumption , or if you're just wanting to save some green and make fewer stops at the pump, then combine both windows down and air conditioning use.
If you're smart about when you choose either option, you'll save a little bit of gas and stay cool while doing it, too. For more information about fuel efficiency and other related topics, follow the links on the next page. Sign up for our Newsletter! Mobile Newsletter banner close. Mobile Newsletter chat close. Mobile Newsletter chat dots. Mobile Newsletter chat avatar. Mobile Newsletter chat subscribe. Fuel Efficiency. Hybrid Technology. If you're concerned about fuel economy, when if ever does it make sense to use your vehicle's air conditioner?
When to Use Your Air Conditioner " ". It depends on your driving speed, but there are times when using the air conditioning system in your car can be more fuel efficient than rolling the windows down.
When to Roll the Windows Down " ". There are times when it's more fuel-efficient to drive with the windows down -- and the fresh air feels pretty good, too. What is my vehicle's air pollution score? What is my vehicle's greenhouse gas score? What is the emission certification standard? Sources Arthur, Dani M. July 22,
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