Audi's 4.2-liter V8 is a terrific engine, delivering smooth and refined power to all four wheels at all times. Nail the throttle, and it roars with authority with a note that's pure music to the enthusiast's ears. The penalty for dipping into the A8's 350 thoroughbreds is predictably poor fuel economy – we got just 13.6 mpg in the city. On the highway at 75 mph, the A8 returned a far more impressive 24.3 mpg. The six-speed Tiptronic automatic delivers clean shifts in normal mode, cuts overdrive and holds revs longer in Sport mode, and responds quickly to manual inputs when using the separate shift gate or the small paddles on the steering wheel.