Chevy Cruze. Its 1.4-liter turbocharged four-cylinder is lighter and more powerful than the Fiesta and it, too, should deliver 40 mpg on the highway, clearly the leading vehicle in the compact class. Other winners are likely to be as follows: Ford Fiesta. Its 1.6-liter four-cylinder engine already provides best in class (subcompact) fuel economy, 40 mpg on the highway or 33 mpg combined. The Volt may also edge out the Prius although it is an electric car with a supplemental gas engine. Figure that the Leaf's equivalent fuel economy numbers will be in excess of 100 mpg when the calculation methods have been finalized. Come December, the pure electric Nissan Leaf and Chevrolet Volt will debut, with the former expected to dethrone the Prius. The top fuel efficient cars will once again be hybrid models with the Toyota Prius retaining its position for a few more months. Automakers can call whatever comes out in a calendar year the following year's model year, even if the car goes on sale on January 1. I say "updated" because the 2011 models have been released throughout 2010, with the last of them expected to roll out in December. Over the coming weeks, the fuel economy numbers will be updated to reflect the release of the remaining 2011 model year vehicles.