The 2015 Nissan Altima is a midsize sedan available in 2.5 and 3.5 model series. The Altima 2.5 has a four-cylinder engine that makes 182 horsepower and returns 31 mpg. The Altima 3.5 has a 270-hp V6 rated for 26 mpg. Trim levels range from the base 2.5 to the upscale 3.5 SL. The Altima seats five people and provides 15.4 cubic-feet of cargo space. Changes for 2015 include comfort enhancements for several versions of the Altima and added safety features for the 3.5 SL model.