Most of the 2012 Infiniti M sedans aren't especially green in any way. With fuel economy ratings that range from 16 to 18 mpg in the city, and 23 to 26 on the highway, neither the V-6 M37 nor the V-8 M56 are particularly frugal. The all-wheel-drive models lose up to 2 mpg, as well, with the M56x at the bottom of the numbers, at 16/23—in other words not really any better than a large, three-row crossover.
Gas mileage is 16/25 mpg with the V-8 and rear-wheel drive, 16/23 mpg for the V-8 AWD—decently improved figures for a car that weighs between 3858 and 4224 pounds.
Until this model year, Infiniti didn't have any hybrid or diesel model for more green-conscious shoppers; but new for 2012 is the M35h, an advanced hybrid sport sedan that achieves EPA ratings of 27 mpg city, 32 highway, without a significant loss in performance.
On the other models, there's also an "Eco Pedal" feature that gives haptic feedback when it senses the chance to save fuel—but most drivers who know enough to buy an Infiniti will know how to best the city fuel-economy numbers.