Is it true that turning on the A/C in your car with windows closed is fuel efficient than windows open A/C off

Question

due to wind resistance.

How much fuel do you save either way. Please share your experience.

Answer 1

If you're going fast, it is better to use A/C, if you're going slower, rolling the windows down is best.  Remember that air resistance is not linear.  That is, if you go twice as fast, you don't have twice the air resistance, you actually have more like 4 times the resistance.  Once you get to about 35-40 MPH (depending on your vehicle), the extra drag caused by having the windows down becomes a greater drain in energy to your car than having the A/C on.

Answer 2

BAD: using A/C.

BAD: windows down at high speed.

GOOD: windows down going slow in town.

GOOD: windows up, A/C off, blower on high.

Trouble is, most people who use A/C blast it and turn their car into a refrigerator and that's very wasteful.  It's true that windows down+freeway is bad too, but that doesn't make A/C good.

If you must use A/C, use it as little as you can bear.

Answer 3

Having the windows open is more efficient under 45mph. Anything over that it is more efficient with the A/C on. In any case modern vehicles have efficient A/C's so it does not take much to run them. You may get about a 2 percent increase following that. The best thing you can do is slowly accelerate from a stop, try not to brake, if you see a red light just let off the gas the second you see it coming up,  keep your speed as close to 55 when you are on the highway and as close to 45 when you are on surface streets, dont gun it through yellow lights, and just try to "feather" the gas pedal as much as possible. Over the last 4 weeks that is what I have been doing and my gas mileage has gone from 16.8mpg overall to 19.8mpg  for close to an 18 percent gain in mileage, and that is close to 20mpg in a 2005 chevy silverado which has a 18mpg highway and 15mpg city. That 19.8mpg is city/highway combined.

Answer 4

It just depends how fast you're going.

If you're going fairly slow, rolling the window down won't create very much drag.  If you're going faster, there will be more drag and it's more efficient to use the A/C.

The cutoff point for where it's more energy efficient to use the A/C is somewhere around 45 mph.

Answer 5

I've heard - you waste gas when you have the windows open - save gas by using the AC -- not much difference but cars are much more aerodynamic than they used to be

Answer 6

It depends on the circumstances. you are going to hear alot of people quoting the Myth Busters Experiment, but they only tested 2 scenarios:

1: windows all the way down on minivan doing 45mph.

2: windows up with AC on in minivan doing 45mph.

In that experiment it was more fuel efficient to keep the windows rolled up and just run the AC because of the drag.

However, in my case, I have a sleek car with little drag and i roll my windows down about 2-3 inch and pop the sun roof up a few inches and I get a very nice draft throughout the car with very very little drag. So in my opinion, if you crack your windows and get a nice draft without fully opening them, it will be more fuel efficient to turn off your AC.