As is the case with many of the more fuel-efficient vehicles that have three rows of seating, whether or not you consider the 2013 Acura MDX to be at all green depends on how much you're using its capabilities. But even then, it's hard to figure this as a green pick at all once you look at the numbers for it versus rival models.
The MDX gets an EPA-rated 16 mpg city, 21 highway. And in its class, there are a number of vehicles that get one or two more miles out of a gallon, which adds up over the entire course of a year—and the time of ownership.
The Lincoln MKT now manages 17/25 mpg, for instance, while the Lexus RX 450h—a Hybrid—gets up to 32/28.
It's also worth keeping in mind that the MDX required premium gasoline.