From the experience of our editorial team, the A7 is pretty green if you can restrain your throttle foot. Over about 120 miles of driving in mixed, mostly relaxed driving conditions, we saw an average of nearly 22 miles per gallon. However we noticed that our average dipped significantly whenever we dipped into the supercharged engine's power reserves; another editor averaged well under the 18 mpg city rating in more enthusiastic combined driving.
If you're okay with a model that's more conservative in appearance and feel, the E350 Bluetec gets an EPA 33 mpg highway. And while there's no confirmation that a diesel A7 is in the works for this side of the pond, Audi has also announced that its A6 will come to the U.S. in TDI form within the next two model years.
It's also worth noting that the A7 manages just 1 mpg better overall than the larger A8 L sedan, which has a considerably roomier interior and much more backseat space.