www.SmartCarCents.com - Which is more efficient- driving on hwy w/ windows down, or AC?

Which is more efficient- driving on hwy w/ windows down, or AC?

I know that having open windows causes drag, which reduces gas mileage, but driving with AC on reduces gas mileage, too. Which is more efficient?

Myth-busters did an episode about that very issue. It was determined that below 45 mph windows down A/C off. Above 45 M.P.H. windows up and A/C on 45 M.P.H. was their threshold for fuel economy in that test series.
Driving with AC on and windows up. On highway more efficient gas mileage. On city streets windows down with AC off.
According to mythbusters, AC is more efficient if you are traveling over 50mph. However, the results should slightly vary depending on what kind of car you have.
If the air outside is at the right temperature, then we should be able to turn off the AC, roll the windows up, keep the fan on, turn the knob to fresh air(not recycle), adjust the vents properly and keep the inside temperature to coldest(blue). We will then save on gas and reduce drag.
ac going down the road at 35 mph or faster. if you going 35mph or less or in stop and go traffic no ac.