The S6 is powered by a twin-turbocharged 4.0-litre V8 that’s shared with the Bentley Continental GT and Audi RS6. In this guise, it develops 444bhp – exactly the same as the RS4 and RS5, and 30bhp more than the pre-facelift model. It’s enough to shove the saloon S6 from rest to 62mph in a scant 4.4 seconds( the Avant takes 4.6) and both will hit a( limited) top speed of 155mph. Twin-turbo torque means the mid-range is just as impressive, and papers over the cracks in the seven-speed gearbox’s talents.