General Question

chill_out's avatar

Does driving with the windows open affect your MPG?

Asked by chill_out (116points) June 17th, 2008

I thought of this when driving from NY to the Jersey Shore and it seemed as though I expended more gas with the windows open, specifically on the highway. I would think it would have something to do with the wind creating a parachute-effect inside the car…. Any truth to this?

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10 Answers

marinelife's avatar

The Mythbusters say computers show windows up and a/c on is more efficient than windows down and a/c off.

syz's avatar

I have absolutely no scientific proof to back this up, but I’m pretty sure that Click and Clack have quoted studies that show windows down with no AC takes as much energy as running the AC. Apparently streamlining the car design only works if the windows are up.

Harp's avatar

Yes. Driving with the windows open at city speeds (<40 MPH) increases fuel consumption by up to 10%. At speeds near 55 MPH, the increase in consumption approaches 20%

Given that AC ups consumption by about 10%, you’re better off with the windows down and AC off at low speeds, but the opposite at highway speeds.

gooch's avatar

Yes it acts like a parachute catching the wind creating more drag therefore you expend more gas

delirium's avatar

It creates a lot of drag, depending on the car. So yes. (Makes me love my car all the more. The rear view window comes down in it. It doesn’t up drag, but gives me just enough of a breeze to be comfortable. )

chill_out's avatar

What a great feature! What kinda car is that you drive if ya don’t mind me askin?

delirium's avatar

its a del sol. :)

gooch's avatar

My Avalanche does that also

ninjaxmarc's avatar

delirium: makes me miss mine even more, weather has been nice to have the top off.

Definitely causes drag to lose mpg.

delirium's avatar

my sympathies. Its hard not to fall in love with the little things. I dunno how I’ll react when I have to let mine go. It already has lost the air conditioning. I’m afraid of what’s next to go.

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