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When driving, is it more fuel efficient to roll down my windows or use the air conditioner?

I was driving across the country during the summer, so I needed to cool the interior somehow. Rolling down the windows causes a loss in fuel efficiency due to increased drag, but turning on the AC also consumes fuel. Which is the more fuel efficient way to cool my car? Thanks!

Public Comments

1. John Stossel of 20/20 says it's more fuel efficient to roll down your windows, whatever your speed.
2. Use the air conditioner. The windows create a large amount of turbulence, and that eats gasoline.
3. THERE IS NO DIFFERENCE THEY TESTED THIS MYTH ON MYTHBUSTERS AND FOUND IT TO BE NO DIFFERENT
4. Hi. Mythbusters did a thing on this and they found no difference, but they were not particularly accurate in their method. The A/C can be pretty efficient.
5. Depends on the speed. If you are at or close to highway speeds it is more efficient to ride withe windows up and with air-conditioning. if you are going slow then the windows are more efficient.
6. Air conditioner. Check out Mythbusters on the discovery channel. They may have a web page, but they showed that AC is more economical. They also did a thing about whether or not it is more economical to put down the tailgate on a truck or leave it up. Turns out, leaving it up is more economical because it helps create an air pocket that aides in minimizing resistance.
7. Turn on your AC and put down your windows...
8. My understanding is the same as Bob's above. On the highway, the A/C is better. At slower speeds, roll down the windows.
9. If you're driving on the highway, the a/c is better. If you are driving slowly then ofcourse the open window is better.
10. I'd say rolling down the windows does cause drag but saves the use of the ac. You will probably find that with gas prices the way they are nowadays that walking is the MOST fuel efficient. lol But yeah...I have found that not using ac in summer is probably the most efficient.
11. Just drive naked with the windows up and the fan on. If it gets too hot hit the a/c button.
12. Good question. If you want to run your car cool in summer then you must spend an extra fuel which obviously the car designer would have considered which does have a specific fuel consumption. On the other hand if you dont want cooling and roll down your windows even then the design facilitate to handle & overome the drag for which also there will be specific fuel consumption. The later one would be giving you more fuel efficient driving than the former one. But you want to run it fuel efficient and at the same time cool then the choose the former one.