A figure of speech. Obama tightened up the standards to where every tiny addition to fuel mileage had to be tried. If Bush is re-elected he will likely slacken off on the CAFE figures. like Ronald Reagan did.
Where I live trucks outnumber cars and he average vehicle has nearly 300 HP. US carmakers are having a rough time getting their fleet average up. In Europe Mercedes uses its Smart Cars to drive their fleet average consumption down.