Audi S6 saloon review

The Audi S6 is a high-performance version of the Audi A6 executive saloon. It used to come with a 444bhp 4.0-litre V8 petrol engine but for the latest model it was replaced by a 339bhp diesel. Yet, with performance-boosting mild-hybrid technology and lashings of torque, it's very nearly as fast, and sharper to drive - even if it doesn't sound quite as good.

Amazingly, it’s not the fastest A6 variant you can buy – that honour goes to the 592bhp Audi RS6, which still uses a thumping twin-turbocharged V8 petrol engine. The RS6 is only available as an estate, though, while the S6 comes as a saloon or Avant estate. The S6 is also around £20,000 cheaper than the RS6 and many will prefer its more demure looks.

As long as you can afford to buy and run it, there’s very little not to like about the Audi S6. The similarly powerful BMW 5 Series 540i xDrive has sharper steering and offers more driver involvement and has fuel-saving mild-hybrid technology.

The Audi S6 is expensive, particularly in range-topping Vorsprung form, so unless you really enjoy attacking twisty roads, the cheaper Audi A6 50 TDI will likely suffice and the BMW is also quite a bit cheaper.

While many are turning their backs on diesel, Audi still sees a future for the fuel, including in its more powerful cars designed to cope with longer journeys. Thanks to its new engine and 48-volt mild-hybrid system, the Audi S6 can now cover around 550 miles between service stations, which is sure to prove desirable.

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It's still reasonably pricey to run, though, with an official fuel consumption figure of up to 40.4mpg for the saloon, falling to 39.2mpg for the S6 Avant estate. Meanwhile, CO2 emissions of 184-189g/km place all versions of the S6 firmly in the top Benefit-in-Kind banding for company-car drivers. This is despite fuel-saving features like stop-start and coasting as you decelerate.

Road tax will cost £140 a year, but a price tag in excess of £40,000 means a surcharge of £325 will cost the owner £465 in the first five renewal years.

Fuel and tax will be expensive, then, and so will other running costs: tyres, brakes and general maintenance for heavy performance cars like the S6 tend to hit hard, although Audi’s fixed-price servicing plans will make the bills easier to predict.

On all but one type of road, the Audi S6 triumphs. In town it’s docile and easy to manoeuvre, on motorways it’s genuinely hushed, while on A-roads the staggering performance and prodigious four-wheel-drive-enhanced grip ensure few cars will be able to keep up. Going from 0-62mph takes five seconds in the S6 Saloon, with the estate taking 5.1 seconds.

If winding B-roads are your thing, however, you may wish to look elsewhere: the S6 is sharper and more agile than before - especially with four-wheel steering fitted - but it's a large car and the automatic gearbox can be a bit slow to respond when you demand snappy changes.

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This aside, the S6 delights. Put your foot to the floor (or close to the floor) and you’ll be thoroughly pinned back in your seat by the acceleration. The 3.0-litre TDI diesel features an electric compressor that can instantly send boost to the engine, virtually eliminating lag. Instead it surges forward in a manner that would leave most hot hatchbacks trailing behind.

Of course, we miss the exciting noise of the old engine, and Audi has fitted a sound generator to compensate, along with fake exhaust tips. Unfortunately, it just didn't sound natural to our ears and we quickly turned it off.

The Audi S6 is just as upmarket as you'd expect, with lovely materials adorning the interior and hugging, electric and heated Valcona leather seats. You also get features like four-zone climate control, keyless entry and a dual-screen MMI Navigation Plus system that's amongst the best in the business.

Refinement is very impressive too, making the S6 a perfect car for long distances. It's even possible to choose double-glazed front windows but in truth the S6 is quiet enough to cover hundreds of motorway miles without them.

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Audi's 12.3-inch Virtual Cockpit comes as standard, ensuring the S6 feels thoroughly cutting-edge, while an optional flat-bottomed steering wheel lends the car a motorsport feel. Other design touches include stainless steel pedals and aluminium door sills with illuminated S logos.

Stepping up to Vorsprung trim adds heated Valcona leather seats, HD Matrix LED headlights, a Bang & Olufsen stereo and adaptive air suspension, but it costs around £17,000.

The whole point of cars like the S6 is to offer sports-car speed with decent practicality. This means you get five spacious seats with plenty of head and legroom as well as a large 530-litre boot (expanding to 1,390 litres), together with split-folding rear seats. Interior oddment spaces and cubbyholes abound, and the Avant offers even more luggage room - between 565 and 1,680 litres.

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Audi has a reasonable reputation on the whole for reliability, and its 21st-place finish in our 2020 Driver Power survey put it well ahead of BMW (27th) and Mercedes (28th) out of 30 manufacturers. A significant 20% of Audi owners reported a fault within the first year, however, with engine and electrical issues the most common.

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Safety is unequivocally strong thanks to the A6’s full five-star rating from Euro NCAP and all S6s come with upgraded brakes to cope with the extra power. Adaptive cruise control (which will accelerate and brake the S6 based on the speed of the car in front) and autonomous emergency braking are available, although you’ll need to spend on optional extras to get the most advanced safety kit.