Better fuel economy?Driving with windows down or windows up and A/C on?What speed might be better for each?

Question

I have a basic sedan(Civic) and Minivan and I was just wondering just how much of a reduction in fuel mileage for each scenario. I would imagine that once you get up to higher speeds, the drag of the open window vehicle would induce worse fuel mileage than a vehicle with the windows closed and the A/C on.

Answer 1

One is less likely to have the window cranked fully open when doing 70 than when doing 20, right?  I don't like to be hammered constantly by a 70 mph wind, but that is just me.   A crack will do just fine and no there would not be a heck of a drag on a crack.   AC draws the same whether you are doing 70 or 20.

Answer 2

Not much. If you've watched Myth Busters, there was an episode tackling this.

The results were not significant so they concluded that driving with or without A/C, windows up or rolled down, won't matter.

Answer 3

You have answered most of your own question. It is TRUE that windows down creates drag and is only suitable in LOWER speeds. AC is ideal for freeway driving and so on. Some experiments and tests have shown that there is not that big of a difference b/w the two. The most important ways to save fuel while driving are dependent on your driving techniques and the condition of your car. Keep your car clean and maintain it properly and regularly and adopt a smooth driving style (avoid hard braking and acceleration, etc). The other part of saving fuel is to drive a more fuel-efficient vehicle which you already have done. The Civic and your minivan are more fuel efficient than other cars, trucks and SUVs. So just follow those simple rules and hopefully we'll all get through these high fuel prices.