Yeah I get about 4 more mpg with the windows down than I do when the A/C is on.

 

I've been getting 25 miles per gallon with the windows down, if I use the a/c for long periods of time i get about 18 mpg. I doubt that having your windows down would produce enough lag to lower your mpg. It never hurt my times at the strip having my windows down, I got a 15.8 when I forgot to put them up.

 

It depends on where you're driving. If you're just driving around town at low speeds, having your windows down and A/C off is obviously much better. However, if you're going 80mph down the interstate, then A/C on and windows up is *MUCH* better on your mpg.

 

Yeah you have to be driving at higher speeds for the windows to create lag. When they did the experiment they did it in an SUV going around a Nascar track. They weren't going incredibly fast, probably at highway speeds.

I'll agree with patterrr, windows for around town, A/C for a highway trip.

 

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