Great expectations frequently lead to dissatisfying realities, and so it is with the Audi S8’s 5.2-liter, 450-horsepower V-10 engine. We knew it was a gas guzzler, and it proved so with an average of 13.9 mpg during a week of spirited driving, but in return we expected the S8 to accelerate in a decidedly quicker fashion than the A8 4.2 we drove a few weeks prior. By the seats of our pants, it did not. The 6-speed Tiptronic transmission usually behaved itself, but sometimes during city driving delivered a bigger dose of off-the-line power than requested. During hard driving on back roads, manual shifting produced fast gear changes using the selector or paddles mounted to the steering wheel.