2007 Audi S6 in Plano

A big engine in a mid-size car--it's been proven to make our glands swell and our mouths water at least since Pontiac stuffed a 389-cubic-inch V-8 into the 1964 Tempest. Today, the German premium brands are its most fervent practitioners, putting tarmac-peeling power into almost-stock-appearing, mid-size sedans. This summer, two newcomers, the V-10-engined Audi S6 and the Mercedes-Benz E63 AMG, will attempt to dethrone the current four-door king of the fast lane, BMW's awesome M5.

To challenge the M5's V-10, the S6 packs a V-10 of its own, but the Audi is able to extract only 435 hp, compared with 500 hp for the BMW. The S6 acquits itself better in the torque department, besting the M5's 384 lb-ft by 14 lb-ft. Mercedes comes the most prepared, at least on paper, with a normally aspirated, 6.2-liter V-8 that delivers a massive 507 hp along with 465 lb-ft of torque.

On the road, these differences in power and torque are less obvious than expected. After all, it's not only the numeric potential that matters but also what you can do with it. According to their manufacturers, the E63 can storm from 0 to 60 mph in 4.3 seconds, and the S6 performs the act in a less explosive 5.1 seconds. Our test results for the M5 put it right in between at 4.7 seconds. Of course, in the wet, the all-wheel-drive Audi wins the stoplight grand prix without even trying. On the autobahn, all three cars will beat the train and challenge the plane.... Read full article