I found this through Yahoo! I thought it was interesting because I have been using my AC alot already this summer and have noticed a significant decrease in gas mileage.

http://www.slate.com/id/2194536/?y=1

 

i dont have a/c so nothing to worry about. lol. gotta love that florida heat...

 

lol, yeah man its hott as ***** here. I try to keep my windows rolled down as much as possible to save on gas but sometimes its just hot air blowing in and the AC has to come on.

 

Here's my custom a/c.

 

Mythbusters did that one awhile ago. They got 2 identical trucks, with an exactly identical amount of gas in the tank and drove around a track. One with the windows down, one with the AC on. AC won, they figured due to drag with the windows open. either way, with an 89, the AC ain't the greatest, so on really hot days, it usually ends up being a bit of both. I also added a rear slider which helps circulate the air.

 

also on mythbusters they said that the difference between the two was only a few miles per tank

 

Nice fan Sean...yeah I didnt really think it made a considerable distance but these days if you can add a couple miles on to a gallon then its worth it. I like driving with my windows down around my town and community but when im on the highway its AC all the way. Inevitably the only people who are going to beat the gas prices are the Amish and thats just because they drive horses instead of cars. I bet there pretty pissed that were turning corn into fuel now which makes the grain they have to have to keep there horses alive go wayyy up.

 

I drive with my windows down alot out here because although it usually gets in the mid 80's by early morning, there's no humidy and usually a nice breeze blowing.

I actually ran my own test about a year ago doing all highway miles on a long trip. Ran 1 tank windows down and 1 tank with AC on. There was virtually no difference between the mileage I got in those 2 tanks so I don't think it really matters.

 

i have tried to see if there was a difference in my truck with ac on or off.. dont really see a difference. 2008 screw with 4.6
I have alwasy heard that for open road ac, if working properly, shouldnt be a difference compared to the wind drag.
Just depends on vehicle i suppose.

 

truth be told in an older truck like a 93 like mine its just as easy to roll the windows down and be happy atleast in my truck i see better milage that way