The 2007 Infiniti QX56 is available as a 4-door, 7-seat sport utility. Starting at $53,050, the 2007 Infiniti QX56 4x4 is powered by a 5.6L , 8 -cylinder engine mated to an automatic transmission that returns an EPA estimated 13-mpg in the city and 18-mpg on the highway. The top of the line 2007InfinitiQX564x2 , priced at $ 49,950 , is powered by a 5.6L , 8 - cylinder engine mated to an automatic transmission that returns an EPA estimated 13-mpg in the city and 18-mpg on the highway.