A/C on or Windows Down? Which is BEST to Save on Gas?!
Driving with the windows up and the air-conditioning on gives a car better gas mileage than rolling the windows down -- or so we've been told for years. But despite this advice, car owners continued to report that their miles per gallon (MPG) actually dropped when driving with the AC turned on.
What's the best way to improve your car's MPG on hot summer days? Look at what the experts say and you'll understand how your car's gas mileage changes on warm-weather trips -- the answer may surprise you.
Bad Gas Mileage Is a Drag
Your car's drag is the amount of resistance it has to the air moving across it as you drive. Cars that have a shape that's long and lean (like a canoe) have less drag -- and usually get better gas mileage -- than a car or truck with a big, boxy shape.
Driving with the windows down does change the amount of drag on a vehicle -- but only a little bit. A lot depends on your car's size, shape and speed. If, for example, you drive a big SUV, rolling your windows down won't really alter your car's air drag much, since it already has so much drag. But if you drive a small, sleek roadster, rolling the windows down will increase your drag by a relatively large percentage, like around 20%.
The other important factor is your car's engine, and how much work it has to do to run the air-conditioning unit. Little 4-cylinder engines have to really crank when they're also running an AC unit. A big 8-cylinder engine, which you'll usually find in larger cars, can run an AC unit without breaking a sweat.
AC and Windows: What the Experts Found
Auto experts from Edmunds.com and the Society of Automotive Engineers (SAE) have run tests to see which strategy -- windows up, AC on or windows down, AC off -- yields better mileage. In an oft-cited SAE study from 2004, engineers compared two large vehicles' fuel efficiency -- an SUV with an 8.1 liter, 8-cylinder engine, and a sedan with a 4.6 liter, 8-cylinder engine -- under each driving condition at low, medium and high speeds.
Both vehicles got the best gas mileage when their AC was off and the windows were rolled up (this is, of course, only an option on cooler days). When the windows were rolled down, fuel efficiency dropped, especially for the sedan with lower drag -- it didn't affect the SUV as much, because the SUV already had a lot of air drag. And when the air-conditioning was turned on and the windows rolled up, fuel efficiency was at its worst, despite the vehicles' big engines.
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What's the best way to improve your car's MPG on hot summer days? Look at what the experts say and you'll understand how your car's gas mileage changes on warm-weather trips -- the answer may surprise you.
Bad Gas Mileage Is a Drag
Your car's drag is the amount of resistance it has to the air moving across it as you drive. Cars that have a shape that's long and lean (like a canoe) have less drag -- and usually get better gas mileage -- than a car or truck with a big, boxy shape.
Driving with the windows down does change the amount of drag on a vehicle -- but only a little bit. A lot depends on your car's size, shape and speed. If, for example, you drive a big SUV, rolling your windows down won't really alter your car's air drag much, since it already has so much drag. But if you drive a small, sleek roadster, rolling the windows down will increase your drag by a relatively large percentage, like around 20%.
The other important factor is your car's engine, and how much work it has to do to run the air-conditioning unit. Little 4-cylinder engines have to really crank when they're also running an AC unit. A big 8-cylinder engine, which you'll usually find in larger cars, can run an AC unit without breaking a sweat.
AC and Windows: What the Experts Found
Auto experts from Edmunds.com and the Society of Automotive Engineers (SAE) have run tests to see which strategy -- windows up, AC on or windows down, AC off -- yields better mileage. In an oft-cited SAE study from 2004, engineers compared two large vehicles' fuel efficiency -- an SUV with an 8.1 liter, 8-cylinder engine, and a sedan with a 4.6 liter, 8-cylinder engine -- under each driving condition at low, medium and high speeds.
Both vehicles got the best gas mileage when their AC was off and the windows were rolled up (this is, of course, only an option on cooler days). When the windows were rolled down, fuel efficiency dropped, especially for the sedan with lower drag -- it didn't affect the SUV as much, because the SUV already had a lot of air drag. And when the air-conditioning was turned on and the windows rolled up, fuel efficiency was at its worst, despite the vehicles' big engines.
[CLICK HERE] to read more
Article brought toyou by About.com
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