Audi A6
Audi made a high-performance, 4.2-litre V8 engine (parts code prefix: 077, identification code: AEC) with a Bosch KE-Motronic ECU available as an option in the original European S4s, and made the decision to continue to do so with the S6, making a version of the 4.2 available as an optional upgrade over the 2.2-litre inline five-cylinder turbo. Unlike the five-cylinder turbocharged version, the V8-powered S6 was supplied with a four-speed automatic transmission as standard, but kept the quattro four wheel drive. A six-speed manual gearbox was also available as an option.
Audi A6
It was powered by another version of the 32-valve (four valves per cylinder) 4.2-litre V8 engine (parts code prefix: 077, identification code: AHK, later to be seen in the Audi S8 as AKH). Audi's performance division reworked key parts of the engine, increasing the maximum power to . It was only available with a revised six-speed manual transmission (parts code prefix: 01E, identification code: DGU) (gear ratios – 1st: 3.500, 2nd: 1.889, 3rd: 1.320, 4th: 1.034, 5th: 0.857, 6th: 0.730), with a final drive ratio of 4.111.