To Ford's credit, it offers a base Mustang with a V-6 engine producing 302 hp that gets 19 mpg city/31 highway. Move up to the top-of-the-line Shelby GT 500, howver, and the engine capability goes up to 550 hp, while the mileage sags to 15 mpg city/23 highway -- and that's with a manual transmission. Still, that's good enough to avoid the federal gas guzzler tax, which requires a minimum of 22.5 mpg.
