Which uses more gas when driving a car at 40 mph--with windows open or closed with a/c on?

Ben Jeepin

It would be the same.

Rod

Windows open will use more fuel every time

goosecrossing

a/c on uses more gas...not by much, but is it worth all that sweat?

lakeguy2302

All of those scenarios are complete myths. Running yor A/C, or havng your windows open or whatever else, has virually no effect on your mileage at all. It's just a myth. I can't believe there are people wo still beleive this. Do you pull forward through other parking spaces in the parking lot to "save on reverse" too?

Big Matt

mythbusters determined that a car driving with the windows down, used less gasoline vs. the car driving with the air conditioning on. the a/c uses more gas than the drag from the windows being open

John Q

AC uses more

BobSpain

Hi,

living in Spain, I have had plenty of experience to pass on to you...

...at 40 mph I would suggest you would use more fuel by having the a/c on and the windows closed. On average the use of a/c adds around 3-4% to the fuel economy figures.

If you travel above 40 mph, say 50+ mph, the saving would be offest by the wind resistance and turbulance caused by wind entering the semi-closed interior of your vehicle.

Whether you prefer to stay cooler and have the a/c on is, of course, your choice. At 40 mph, the breeze, unless properly directed, may not keep you as cool as the a/c. And, of course at higher speeds without the a/c you may be uncomfortable because of the buffeting the motion generated wind has on your hair and face, etc.

So...if you still can't make your mind up...sorry!

BobSpain

Fred C

At 40 mph, the difference in a modern car will be small, but windows open will use just slightly less gas. You will, of course, be hotter. Above 50 mph, the a/c on & windows shut option will be a little more fuel efficient.

polly_peptide

It depends a lot on your car. Some cars will use more gas with the AC, and some cars won't. The real question is... is rolling down the windows "equivalent" to turning on the AC, and on a hot day, it's totally not.

mircallia

This was on an episode of Mythbusters. They ran different scenarios, with inconclusive results. They finally drove two identical vehicles on a track at a set mph, one windows down the other a/c. The a/c vehicle ran out of gas first.

I thought it was 45mph with the windows open uses more fuel (because of the drag created by turbulence) than using the air-con. But only ABOVE that speed.

Mr. John

What difference does it make? Turn on the A/C and have a comfortable ride.

baby_lover_girl_2020

a/c takes more gas