The 2011 Chevrolet Impala may not have the most up-to-date engines, but in terms of fuel efficiency, they're still competitive.
The EPA rates the base Impala's 3.5-liter V-6 at 19/29 mpg, a surprisingly high figure given the sedan's outdated four-speed automatic transmission. Even with the bigger-displacement 3.9-liter V-6, the Impala can hit 17/27 mpg. The best-in-class Toyota Avalon musters 20/29 mpg.
The Impala's mileage may improve significantly next year, as Chevrolet may replace both drivetrains with a newer V-6 coupled to a six-speed automatic.
The Impala does offer one alternative for drivers looking for other fuel sources: it's E85 compatible, meaning it can run on ethanol blended with gasoline as well as gasoline alone.