If you’re expecting the engine to be clattery, think again; thanks to a trick exhaust, it does a passable impression of a big capacity petrol V8.
True, the S6 doesn’t rev like a petrol, so the BMW 540i and Mercedes-AMG E 53 can both get from 0-62mph faster. However, a time of 5.1sec is anything but slow, and making swift progress is pretty effortless because of the huge torque that's available between 2000rpm and 4000rpm to push you along.
It should be noted that the cheaper 50 TDI A6 makes life similarly easy much of the time and doesn’t feel significantly slower. But the 50 TDI can leave you hanging when pulling out of junctions or overtaking, because the gearbox is so slow to kick down through the gears. The S6’s 48-volt electrical system ensures it rarely frustrates in the same way.
In fact, the eight-speed automatic gearbox contributes to the car’s easy going character, doing a good job of keeping the engine within its ideal operating window. But you do have to put up with quite a bit of road noise, and the S6 never feels especially sporty.
Both the 540i and the E 53 are more agile and deliver greater steering feedback. Smaller performance cars, such as the Alfa Romeo Guilia Quadrafoglio and Mercedes-AMG C 63, are what you need if you're a really keen driver looking for truly effervescent handling.
Where the S6 scores better is for those looking for ride comfort. Fit the optional air suspension (standard on Vorsprung trim) and select the softest Comfort setting and the car wafts along motorways or back roads with considerable aplomb. Things get a little grislier on really battered sections, especially around town, but it’s still one of the most cosseting cars of its type. A word of warning, though: the optional 21in wheels make the ride a lot more crashy.