Brian O'Conner wrote an op-ed in Saturday's Detroit News suggesting we can save gas by leaving our windows up and the AC on:
"According to Bankrate.com, it's best to sweat it out around town, when you're driving at less than 40 mph.In November 2004, the Discovery Channel's Mythbusters (one of my favorite shows) tested that in Episode 22:
"But once you're running over 55 mph, wind drag will lower your mileage by 20 percent or more, so you're better off rolling up the windows and kicking on the AC. At around 45 mph it's a wash, since you've got 10 percent wind drag, experts say."
"Jamie's A/C car ran out of gas first -- Adam's windows down SUV ran for another 30 laps -- completely contradicting the computer mpg estimate. Computer estimate based on air flow into the engine, so it would appear that it is unable to properly model the difference between A/C and windows down."To be fair, Mythbusters had to run at 45 MPH due to a safety officer's insistence, but that was faster than the experts' 40 MPH.
It probably also depends on the kind of vehicle you're driving. If you're already driving something as aerodynamic as a brick like Jeep, SUV or pick-up truck, it probably matters little where your windows are. Turn your AC on full-blast AND leave the windows down for the dog to hang its face out--who cares?