On a hot weather do you save gas by leaving the car window open or just turn on the AC?

a/c uses more fuel.

If you are “in town” leave the windows down…On the freeway use A/C! The wind friction on the freeway with windows down actually uses more gas. In town there isn’t as much.

A/C uses more fuel. Check my link the Mythbusters helped me with this conclusion.

Your better off rolling down the window, using the a/c is using power from the battery and using more fuel.

Melissa is right, Abe you forgot the episode when they relooked at the myth. It went like this. If you are traveling 45mph and under, it is better to drive with the windows down and a/c off. Above 45mph drive with the windows up and a/c on. The reason was that when you reach a certain speed, the wind drag is much greater on the car and therefore it is better to drive with the a/c on when driving above 45mph.

if the a/c works use it !! you will smell better once you get there

All of you are wrong. Having the windows open while driving increases drag, thereby decreasing your gas mileage. Use your A/C, keep your windows up, and cool off and save money.

wrong a/c off all the time saves money (gas).
removing it saves even more.
not buying it in the first place saves all the energy and money wasted in making it in the first place.
driving at 120mph with the windows up and the A/C off saves gas. ( with windows down, right show me ?)
everyone is splitting hairs and looking for compromises here.
it always uses energy if it is hot out.
and anytime the clutch is engaged ,like when you turn on the fast defrost cycle too.
the device is simple. The clutch is either engages or not.
When driving too fast it even wastes more , because it is rotating at a speed way beyond need..

There is a solution coming, that will put a CVT on the pump.
it has more of an effect on small engines the giant ones.
because some giant engines have excess energy at idle and and moderate speeds.
But this topic best fits economy cars.
forget the 500 cubic inch monsters.