Roll Your Windows Down Instead Of Using The AC To Save Fuel

When it comes to cooling down your car, it turns out there's really no more fuel-efficient way to do so than to roll your windows down. Yes, even on the highway.

It's not exactly a surprise that rolling your windows down when at slow speeds uses less energy than the air conditioner. However, as news site Vox points out, common wisdom has held that when you're driving on a freeway, the drag on your vehicle that rolling your windows down creates eliminates any gains you get from not using your air conditioning. Turns out that's not true. Even at high speeds, rolling your windows down still saves some petrol:

For both vehicles, having the AC on (blue lines) was consumed more gas than having the windows down (green lines) at all speeds tested.

The difference was very small for the sedan, and the gap did close even further at high speeds, but it didn't disappear. For the SUV, the difference was much bigger, and actually increased at high speeds.

Of course, rolling your windows down isn't always the perfect option (particularly if you live in a hot, humid place). But if you've got a fuel guzzler and you want to scrape a few extra kilometres out of that tank, turn off the A/C and roll the windows down, no matter where you are.

Why rolling down your cars' windows is more fuel efficient than using AC [Vox]


Comments

    Mythbusters did this years ago.

      Because Mythbusters is just as credible as the Society for Automatice Engineers

        more entertaining, anyways. But it doesn't change the fact that they did it years ago.

    Is very very vehicle dependant. On newer cars with complex aero dynamics drag car be greatly increased.
    And also a lot of cars now run the ac pump permanently.

    It will be 42°C outside today. I will be using the AC, fuel economy be damned!

    So this experiment simply finds that rolling down the windows down causes you to use less fuel than turning on the air conditioning.

    A better study would be to determine what is the best way to cool the occupants of a car down, given outside temperature, humidity, car type and then identify any other variables that might affect the result.

      The kind of people who actually care about so much about this stuff probably aren't as interested in that. They only want to get that extra 3kms out of a full tank for the moral superiority.

    God only knows why the poster has decided to truncate the x-axis label off the picture in this article?

    On the topic of the axis labels - only crazy yanks would put an x-axis in km/hr and a y-axis in gallons/mile. The y-axis also has no values indicated, so it's actually impossible to determine if the fuel consumption differences are significant or not.

    On the topic of fuel efficiency, the original article proves conventional wisdom in my opinion - for a sedan at high speed the fuel efficiency is similar when using A/C versus rolling the windows down. People opt for the A/C at high speed because it's cooler and much quieter and not much worse mileage.

    Save a few kilometres? Is that it? A few kilometres! I get 400km to 450km a tank and winding down my windows will save me a few kilometres... No deal!

    actually Porsche is about to implement something they just tried and experimented with the 918 super car, to great success I might add too
    that car is completely belt less engine/ ancillary wise. and the aircon, power steering etc etc all used electricity generated by the Motor generator unit which is installed exactly where the starter motor used to be. it also has generator units on the brakes so when you are off the throttle and rolling. you are regenerating as well. So this eliminated the extra HP requirements on the engine when these accessories were running. the aircon and power steering needs about 10-15 HP to drive the pumps, belts and pulleys. which is why you get the extra fuel consumption when you turn the aircon on.
    A way to describe it is when you hit the aircon button you essentially make the car go up a slight gradient hill (you require more throttle to maintain the speed)

    Hi all,

    Just want to let all of u guys know that the science is still out on this. I remember seeing a lot of investigations that indicatindicate that e.g. at 100kmh ac is more efficient then Windows down.

    An example ofone such study (though even more scientific ones exist) is this on d one from youtube: http://youtu.be/ue6DsRncyfI

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