With the price of gasoline greatly increasing, "the miles-per-gallon estimates calculated by the Environmental Protection Agency have taken on a new prominence in a nation suddenly intent on squeezing every mile out of its cars," write authors Charles Pope and Lisa Stiffler. However, critics say these numbers are inflating mileage by 15 percent to 30 percent -- and EPA agrees. Since the numbers were last revised in 1985, conditions have changed, including air conditioning being standard and the speed limit increasing from 55 to 70 miles per hour on many interstates. The old number estimates 55 percent of driving time is in urban traffic, when in reality congestion has increased by 225 percent with a parallel effect on fuel mileage. Auto manufacturers feel the current formula works just fine and fear that "the effort to change the mileage formula could be a backdoor attempt to increase the corporate average fuel efficiency -- CAFÉ --standards," write Pope and Stiffler. "Whatever the politics, fuel efficiency results are being scrutinized as never before."