The 2012 Chevrolet Impala is available as a 4-door, 5-seat sedan. Starting at $25,760, the 2012 Chevrolet Impala LS is powered by a 3.6L , 6 -cylinder engine mated to an automatic transmission that returns an EPA estimated 18-mpg in the city and 30-mpg on the highway. The top of the line 2012ChevroletImpalaPolice , priced at $ 27,105 , is powered by a 3.6L , 6 - cylinder engine mated to an automatic transmission that returns an EPA estimated 18-mpg in the city and 30-mpg on the highway.