We've compiled a list of the 10 most fuel-efficient cars currently sold in the U.S. based on the Environmental Protection Agency's (EPA) miles-per-gallon ratings for city and highway travel. We considered only those cars that you can refuel at a regular gas station, so there are no electric or natural gas vehicles on this list. In order to arrive at a final hierarchy, we used the EPA's combined fuel economy formula: 55 percent of city mpg rating plus 45 percent of highway mpg rating. The rating for each vehicle below is expressed in mpg as a city/highway ratio. All ratings apply to base models equipped with a manual transmission, except where indicated otherwise with an asterisk. Also, we only allowed a given model to appear once on the list, except in the case of the Honda Civic because it's available in both gas/electric hybrid and regular gasoline versions.