We’ll start with the negatives. If the RS6’s immensely powerful 4.0-litre V8 disappoints in any aspect, it’s in the way it sounds. There’s a richness and an aggression to its deep, growling timbre that’s eminently appealing when you can hear it, but compared with the more expressive V8 of the Mercedes-AMG E63 and, to a lesser extent, the BMW M5’s, the Audi’s engine just sounds a bit restrained.
Even with the optional RS sports exhaust fitted, the way in which its soundtrack swells into the cabin is akin to listening to a favourite music album from another room. In this sort of car, you’d just prefer to be able to hear it in more detail and at apparently closer range.
The other slight sticking point is that we averaged just 19.5mpg during our time with the car – a figure that dropped to 9.8mpg during performance testing. Allowing for the fact that this engine develops 591bhp and the car weighed 2.2 tonnes on our scales, fairly extreme fuel consumption isn’t exactly a surprise. However, it does erode the car’s everyday ownership appeal a bit and reveals that Audi’s economy-boosting measures will have a rather limited effect should you choose to stretch the car’s legs.
And you will – because on summer tyres and a dry track, the Audi’s appetite for speed is even more voracious than its need for fuel. The RS6 lunges off the line with incredible ferocity, although it takes a couple of runs and a bit of heat in the tyres to launch it completely cleanly. Initially, the rearward weight transfer as the car springs forward can make the front wheels momentarily scrabble for purchase, but from there on out, the rate at which the Audi accrues pace is nothing short of incredible for a car of its size. Excessive? Probably. Unnecessary? Without question. But, above all else, utterly spectacular.
Our test car hit 60mph from a standstill in an average time of 3.3sec. The run to 100mph, meanwhile, was dispatched in 7.8sec. So it’s a match for the M5 up to 60mph, although the lighter BMW pips it by 0.3sec to 100mph. And while the Audi’s in-gear performance is certainly strong (30-70mph in fourth took 4.6sec), it’s still not quite as quick as the M5’s 4.0sec effort. Either way, you’d have a very hard time convincing anyone that the RS6 needed more grunt.
The eight-speed gearbox is well mannered. Aside from a slight tendency to shunt a bit at step-off, it changes gears swiftly and smoothly when up and running. The carbon-ceramic brakes, meanwhile, can be a bit grabby at low speed, but their power and robustness when you really need them is unquestionable, as our braking test results clearly show.