Better mileage with a/c on or windows open?

Question

With the price of gas going up as fast as the temperature,I need to know if I get better mileage with one or both windows down or with the air conditioner on? I drive a '96 Nissan Sentra with a rebuilt '99 engine and the cost of gas is killing me. (But I hate to sweat!)

Answer 1

Popular Mechanics also did several tests on this and came to the conclusion that the drag created by the windows down - above approx. 40 mph - creates more of a need for gas to push against it (think running with a parachute on - you've gotta run harder and burn more calories to keep the same speed).

So: under 40mph, windows down is more efficient; over 40mph, A/C is more efficient.

Answer 2

Shifty67 provided the perfect answer so a thoughts (provide him the ten pts), yet i needed to operate some issues: each vehicle behaves in a special way aerodynamically, by using their diverse shapes. some vehicles will be extra impacted through having the homestead windows down than others. also, drag is a function of the sq. of the vehicles velocity, so wind resistance is going up dramatically at street speeds. the final consensus is that above 40 5 mph, drag hurts economy better than A/C does.

Answer 3

Mythbusters evaluated this concern and drove two SUVs on a track in a controlled environment and proved that their was virtually no difference in economy. In fact, the numbers favored the car with the windows down, although minimally. Personally, I just prefer to ride in comfort when I drive, so I use the AC.

Answer 4

The Discovery channel did a bit on this, on Mythbusters. I believe the answer was with the windows down and the AC off.

Answer 5

Your car will use more gas with the AC compressor on, versus the windows open..... I have noticed this for the last 27 years of driving..... you use less gas with the windows open and AC off.

Answer 6

both create drag which is the lesser of the two evils is hard to say. either way you won't get the mileage you should under either circumstance. city driving windows down won't make much difference but on the highway another story.

Answer 7

I once read that 35 mph was the threshold...above and its better to use the ac as windows down slows your car down resulting in the engine having to work harder. Below and you're better off using no ac.

Answer 8

It depends. Windows down is more efficient at low speeds, but the aerodynamics introduce drag at high speeds. Somewhere around 40 MPH is the cutoff.

So around town, windows down... Cruising down the freeway, run the AC.

Answer 9

i havent seen that episode of mythbusters but its better to drive with the a/c at higher speeds because driving with the windows down will create drag in the car an low speeds with the window down

Answer 10

55 and above Mythbusters says use the Ac below 55 open the windows.