In order to keep cool in the summer while driving what provides the best fuel economy: having the air conditioner on or leaving the windows open?
I can’t offer a link for a cite because I don’t feel like searching the Car Talk site for the podcast. But on a program where this question was asked the brothers agreed that for maximum fuel economy, under 45 mph they recommend windows down and AC off. Over 45 mph, windows up and AC on.
How about maximum efficiency: Windows up and no A/C at all 
Yup, that’s how I roll, except AC really isn’t needed in AK. So it’s a win win. Could always go old school and mount a swamp cooler in your vehicle.
Try that in Tennessee, I dare ya.
No, I don’t.
And if you do try it–do you prefer roses or lilies at your funeral? Heatstroke is no good, bub.
It also depends on the vehicle. They are not all aerodynamically equal. Anyone who really has to know can buy a Scangauge II or Scangauge e to monitor the mpg in real time, is the car is a 1996 model or newer.
We really don’t have the option to think about that in Las Vegas.
Years ago, I was driving our Saturn SC2 to work…about a 20-30 minute drive on the freeway. One summer Monday, the AC went out and I wasn’t getting paid til Friday and thought I could wait until then to get it fixed.
Wrong.
Do you have any idea what it is like to get into a car that is probably 180 degrees (sitting in the sun all day) and just rolling down the windows to drive a on freeway? It is like someone has two hair dryers at full blast shooting into your already toasty car.
I found the money and it was fixed on Wednesday.
When it is already over 100 degrees in the mornings, driving without AC is really not an option - and saving 14 cents with fuel efficiency would probably be offset by the cost of hospitalization from heat stroke.