The 2006 Infiniti M45 is available as a 4-door, 5-seat sedan. Starting at $47,150, the 2006 Infiniti M45 Base is powered by a 4.5L , 8 -cylinder engine mated to an automatic transmission that returns an EPA estimated 17-mpg in the city and 23-mpg on the highway. The top of the line 2006InfinitiM45Sport , priced at $ 49,950 , is powered by a 4.5L , 8 - cylinder engine mated to an automatic transmission that returns an EPA estimated 17-mpg in the city and 23-mpg on the highway.