Which wastes more gas: A/C or your windows rolled down?

Question

I have always heard that using your air conditioner while driving wastes more gas. But recently someone told me that having your windows rolled down is worse than having you A/C on when in comes to saving gasoline. My co-worker said she couldn't explain why that is...it just is. Is there truth behind it?

Answer 1

Definitely having the windows rolled down wastes more gas. It makes the car less aerodymanic and creates a drag making the engine run harder. That is the theory anyway... I honestly don't notice a difference in gas concerning A/C verses windows down. Maybe that's just me!

Answer 2

Myth busters did the test. Windows rolled down caused enough drag on the car to cause worse gas mileage then the A/C

Answer 3

A/C wastes more gas.

But not by much, a couple of miles I think.

saw it on  mythbusters two cars were on a track with the same amount of gas and one had windows down, and the other a/c on and the one with ac ran out of gas first.

=)

Answer 4

It really depends on the vehicle, but in general it is more efficient to use the air conditioner in modern vehicles.  The reason for better fuel efficiency stems from the laws of aerodynamics.  When you travel with the windows down, that cool breeze of air coming into the car is also causing drag.  In fact, the breeze that you feel is the wind resistance on the vehicle.  If you have multiple windows open, your vehicle turns into a wind tunnel which the engine has to pull against.  Ultimately the air conditioner does require energy to turn the compressor, but nothing like the varying load (i.e. speed) of the air the vehicle has to cut through with the windows open.  The ideal solution is windows up, and no air conditioning-but that's an uncomfortable ride.

Answer 5

A/C uses less gas

windows down use more because it works against the aerodynamic design of the vehicle

Answer 6

windows rolled down. It creates more drag, wind resistance.

Answer 7

I always thought that if you rolled your windows down that you don't use as much gas as using the air condition.  I know when I don't use my air my gas lasts longer, I only roll down my windows just enough to let air come in.

Answer 8

At higher speeds (generally above 60 mph), rolling your windows down will waste more gas due to the drag force.

At lower speeds, the drag force is a lot less, so using the AC would probably waste more.

Answer 9

I would imagine that there are many veriables to the correct answer, mainly being the type of car, size of the engine, effeciency of the a/c system.  One way for sure is to test it yourself, fill your tank and drive with the windows down and the a/c off, keep track of how many miles you drive.  Then fill your tank again and drive with the windows up and the a/c on, keep track of your miles again. Deciede for yourself which is better. Personally the little it will make a differnce or not, if its hot out,I will run my a/c

Answer 10

the windows rolled down.   It really messes up the air flow around the car and causes a lot of resistance because of the messed up air.

Answer 11

More energy is wasted by asking this question again.

Answer 12

You heard right: it's true that turning on the A/C is better for saving gas than having your windows open. I suggest turning on the fan in the vehicle & limiting the use of AC whenever possible. This is even better than the A/C.

Answer 13

A/C is always bad.

Windows down is bad on the freeway.  

What's good is windows up, A/C off, vent on full.

Now let me explain that.  A/C always uses a lot of fuel, no surprise there.

Windows down only matters if you're going fast.  It's the same problem a bicycle has - at slow speeds riding is easy, but at high speeds the wind cuts you down.  That explains spandex bicycle shorts - seriously.  

Your car has the same problem, but spandex pants won't fix it (thank God!)  The windows down makes the drag much worse, because the air is blowing in the windows!   Now it should be obvious that this is no big deal in town, but at freeway speeds it is much worse - you can't hear yourself over the noise!  So only at high speed, yes, windows down is just as bad as A/C.  

The winning play is windows down in town, windows up and vent on full on the freeway.  If the car is unbearable with just the vent, then give it a shot of A/C for just a few seconds, and go back to vent.

Answer 14

Windows Down, Not for any factual reasons, just because it will be less stressful than arguing with your Spouse about the windows being down and messing her hair. In the end running the AC is worth it just to avoid the fight.