The S6's fenders proudly display "V8 T" badges, while the spec sheet boasts a designation of 4.0 TFSI V8. In English, that means that the S6 is powered by a 4-liter, eight-cylinder engine that is force-fed air by a turbocharger and sips gasoline via a stratified fuel injection system. Power at the crank is estimated at a maximum of 420 horsepower and 406 pound-feet of torque.