Not only is the Toyota Prius the top-selling hybrid vehicle, having recently topped 1 million units sold, but it is also the most fuel-efficient vehicle on the road.

According to the Environmental Protection Agency, the midsize Prius gets 48 miles per gallon in the city, eight mpg more than the runner-up, the Honda Civic Hybrid. Each car gets 45 mpg on the highway.

The EPA's list includes both hybrid and gas-only cars, and rates the cars by category.

The most efficient two-seaters are the Smart Fortwo convertible and coupe, which each get 33 mpg in the city and 41 on the highway. The Smart is produced by Daimler and is new to the United States market this year. The next most efficient two-seater is the Mazda MX-5 Miata, which gets 22 mpg in the city, 27 on the highway.

The Mini Cooper has the market cornered as the most efficient minicompact car. The Mini Cooper with the manual transmission gets 28 mpg in the city and 37 on the highway, while the version with the optional automatic transmission gets 26 mpg in the city, 34 mpg on the highway.

Toyota's Yaris is the most efficient subcompact car, with both the manual and automatic versions getting 29 mpg in the city. The manual gets 36 mpg, one mile more than the automatic version does, on the highway.

The Civic Hybrid is the most efficient compact car, followed by the Toyota Corolla, which gets 28 mpg in the city, 37 mpg on the highway.

The Nissan Versa follows the Prius in the midsize category at 26 mpg in the city, 31 on the highway.

The Honda Fit is the most efficient small station wagon, with both the manual and automatic versions getting 34 mpg on the highway, and the manual getting 28 mpg in the city -- one more mpg than the automatic.