The 2012 Infiniti G37x is available as a 4-door, 5-seat sedan. Starting at $38,500, the 2012 Infiniti G37x Base Sedan is powered by a 3.7L, 6-cylinder engine mated to an automatic transmission that returns an EPA estimated 18-mpg in the city and 25-mpg on the highway. The top of the line 2012 Infiniti G37x Coupe, priced at $40,900, is powered by a 3.7L, 6-cylinder engine mated to an automatic transmission that returns an EPA estimated 18-mpg in the city and 25-mpg on the highway.