Not always, especially when you're comparing with rolling the windows down. Especially in a low drag vehicle, rolling down the windows at speeds above 55 mph will increases the drag coefficient by a significant factor. This means gas consumption is going to be effected adversely. For those of you that drive around with bike on bike racks, those also can kill your fuel economy because of the increased drag.

The Mythbusters on the Discovery Channel did a test, and proved that blasting the AC during high speed travelling is more fuel efficient than rolling the windows down at the same speed. On the other hand, in their first test, they had 2 blocky SUVs do the test, and going only about 45-50 mph. The SUV with the AC blasting ran out of gas earlier.

 

I suck it up. Well, I am really skinny too I dont sweat that much.

 

I live in a valley. Our summer temperatures are horrible when you factor in the humidity. VERY hot and muggy. A friend of mine works for the Foreign Affairs department and said when people from the Middle East Ottawa in the summer, they don't spend that mich time outside because it's too muggy!

In the summer, we can hit 35C = 95F plus humidity. The humidity can make it feel like 43C = 109F very easily. But because of the high humidity levels, your skin doesn't cool you as well, and you sweat. In Arizona, they have a dry heat, so you can still walk around in a suit without looking like a wet spunge.

On the days that I don't drive in the middle of the day (to meetings), I'm usually fine without the AC on.