gas efficiency?

Question

which is better on gas mileage?

driving w/ ac on and window closed
or
driving w/ ac off and window open?

Answer 1

It deals with a combination of forces.

Mythbusters has done this a few times on their show. They basically came to the conclusion (that is a generalization for most vehicles)

That all vehicles have a "break even" point between the forces of drag and the additional cost of energy necessary for the A/C compressor.

Meaning, if you are driving slow, the drag forces are far less than the energy that you are using when you use the A/C.

When driving fast, the drag forces cause you to use more energy to overcome those forces vs using the A/C.

The general conclusion they came to was that for most cars the break even point was around 45 mph.

So if you are drivng slower than 45mph, you will most likely save gasoline by having the windows rolled down.

If you are driving faster than 45mph, you will save gasoline by having the windows rolled up and using the A/C

At 45mph it really doesn't matter as the energy usage will be about equal.

Answer 2

Driving with the windows down is better almost all the time. You'd have to be going very fast for the wind resistance to be enough to offset the A/C usage. This will, of course, vary by what type of car you have, but it's true, by and large for most cars. Mythbusters tested this and found that windows down was better than using the A/C.

Answer 3

ac does not drag as much power from the engine as they used to in years past. But generally over 40 MPH in moving traffic and the windows are better off closed and ac unit on

Answer 4

A/C on with windows closed. It reduces drag on the vehicle holding it back.

Answer 5

window open a/c off they tested this on the show mythbusters