For the 2012 Audi A8, a lightweight structure helps make this luxury flagship more of a miser than you might think. Thanks to that, and lots of efficiency-minded engineering in general, the A8 achieves an EPA-rated 18 mpg city, 28 highway. That's really impressive, and actually better overall than the BMW ActiveHybrid 750Li.
The top-of-the-line W12 model might not provide acceleration that's all that much quicker, but buyers are bound to appreciate the smoothness and flexibility--and probably not care all that much about the ratings, which are 14/21 mpg nevertheless.
We still haven't driven the W12, but grom what we—as well as other auto critics—have seen, the A8 returns impressive gas-mileage numbers in real-world driving; with a lot of stop and go, we still managed an 18 mpg average.