The 2006 Nissan Altima is available as a 4-door, 5-seat sedan. Starting at $17,750, the 2006 Nissan Altima 2.5 (50 State - ) (M5) is powered by a 2.5L, 4-cylinder engine mated to a manual transmission that returns an EPA estimated 24-mpg in the city and 31-mpg on the highway. The top of the line 2006 Nissan Altima 3.5 SE-R (50 State) (A5), priced at $29,650, is powered by a 3.5L, 6-cylinder engine mated to an automatic transmission that returns an EPA estimated 20-mpg in the city and 29-mpg on the highway.