Don’t know how I missed this before but I’ve been assuming that having my A/C on was reducing my gas mileage. Edmonds tested this in Dec 2005 and Consumer Reports recently and both concluded that the A/C does not appreciably affect mileage.
Here are some other items from the Edmonds study about fuel economy.
Joe Duck 
Actually, its air-conditioning off AND windows closed that will save gasoline. Add driving barefoot (at least on the accelerator) and you get further gas savings. Ofcourse you also have an unpleasant drive and get dehydrated.
Professional drivers in the old Mobilgas Economy Run would do this and obtain ridiculous gas milage figures that no ordinary driver would ever achieve but it was great for the advertisements.
Can’t afford to drive? Stay home and play poker until you have won enough to afford it but when you drive, drive comfortably!
Interesting FG – I was wondering if the Windows open increased the drag and thus increased energy used about as much as the A/C increased energy use – your note suggests yes and that makes some sense.
Simple DO The Test!
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feel you r right
it might affect on mileage but it will be marginal