Fuel Economy Tip - Roll the Windows Up
May 2nd, 2006 | by Brian Carr |With the weather being nice, I’m sure many of you wouldn’t mind hopping in the car, rolling down the windows and going for a drive. While that’s not a bad idea, you may want to keep the windows up if you’re trying to get good gas mileage out of your leisurely drive.
Keep your car’s windows up, especially the faster you go.
A car is its most aerodynamic (meaning it moves through the air with less resistance) when the windows are rolled up.
When your vechicle’s windows are down, especially at highway speeds, there is more drag placed on the vehicle. Drag is the force that opposes your car’s movement, so the less amount of drag, the less amount of energy (gas) your car has to use to get up to and maintain speed.
By having the windows down at highway speeds, you can reduce your vehicle’s fuel economy by up to 3%, or roughly add $.09 to each gallon of gas you use! For a 15 gallon car that is filled up once per week, that adds up to over $70 per year.
Especially when the weather is nice (not hot), you should be able to keep the windows up and get away with using a cool vent.
We’ll talk more about using the AC in a following tip.
4 Responses to “Fuel Economy Tip - Roll the Windows Up”
By b3n on May 23, 2007 | Reply
Check out what the mythbusters have to say…
http://kwc.org/mythbusters/2004/11/mythbusters_boom_lift_catapult.html
By John Waiveris on May 23, 2007 | Reply
In my experience, this is false. I cannot see a change on the fuel consumption gauge in my car when I roll up/down the windows. However, I notice a 15-25mpg drop when the AC is on.
By William Wilgus on Jul 9, 2007 | Reply
You really can’t make a blanket statement regarding a/c on or off vs. windows up or down. Which is more fuel efficient depends upon the vehicle and its speed. Generally, the faster the vehicle is going, the more likely it will be that having the a/c on is more fuel efficient: aerodynamic drag increases as the square of speed. Equally important, though, is the engine’s power capability: the increase in power required for a/c with a powerful engine will be quite small as a percentage of power, and therefore any increase with such an engine will likely not make much difference. The opposite is true with low-power engines. Turning on the a/c in my 130 hp / 129 ft-lbs torque 2.0 liter four cylinder very noticeably slows the care down!
By Ayall Sagi on Oct 4, 2008 | Reply
I don’t buy much of his either.
I’m extremly curious about this subject, and wish more explinatinon was available.
First of all… when you’re on the highway, who has ALL the widowns down?
What if you have 1 windown down 1 inch?
How about 1 windown down 2 inch?
How about 0.00001 inch?
I’d like to know some details of the study before i buy in.
And what size of Car? a honda civic or a Ford Explorer?
Does it make a difference?
How about A/C Possition?
If you have A/C on very low or very high?
I’m 100% sure all these effect details are not minor and have a significant effect on the car.
IMO there should be a study which DETAILS each speed, with the ideal driving condition. (example; driving at 65mph in honda civic = drive with windows all the way up and a/c on low)