Aced by the RS4 below it and the RS6 above, the S6 of 2006-2011 never really had its day. It was neither as fun to drive nor as well resolved as its more desirable rangemates, so it melted into the background as just a regular Audi saloon that happened to have a V10 engine under its bonnet. Still, who doesn’t like a big German autobahn crusher, even if the simplest mechanical repair is likely to bankrupt them?
The Audi S6 cost £55,000 new, but today you can pick up an early, high-mileage example from £7000 – not that we’d recommend doing so without first having it inspected by an expert. Crumbling intake manifolds, coked-up valves (it’s a common issue with Audi’s direct injection FSI engines), leaky exhausts and other traps await the S6 novice caught like a rabbit in the headlights.
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Blink and you’d think it was an A6, but closer inspection reveals discreet ‘S6’ badges front and rear and, satisfyingly, ‘V10’ badges on the front wings. Daytime running lights adorn each side of the front bumper air intakes, and neatly integrated quad exhaust pipes complete the picture.
The 429bhp 5.2-litre V10 engine makes 398lb ft between 3000 and 4000rpm, which is high compared with today’s turbo engines. Like the RS4, the quattro drivetrain sends 60% of it to the rear wheels, the rest to the fronts. From 2007 the quattro system gained the later Torsen T-3 limited-slip diff. The gearbox is a solid-as-a-rock, six-speed Tiptronic with paddle shifters. Brakes discs are ventilated front and rear. The fronts, incidentally, are whoppers at 385mm. The model was mildly facelifted in 2009 (it amounted mostly to styling tweaks) but the arrival in 2008 of the RS6 had already begun to suppress S6 sales. Unlike that model, which came only in estate, or Avant, form, the S6 was available as an estate and saloon. Today there are slightly more S6 Avants than saloons for sale. Prices are broadly the same for both, but with its 1660-litre boot, the Avant is the more practical.
Autocar’s reviewer wasn’t exactly blown away by the S6, the engine feeling “neutered of its true potential” (0-62mph in 5.2sec just didn’t cut it). Meanwhile, they noted, the car’s overly firm ride revealed every surface irregularity. At least if your chosen S6 feels the same, you know its springs and suspension bushes are holding up. On a more positive note, our reviewer praised the security of the quattro four-wheel drive system. It’s a heavy car but it should brake powerfully and straight.
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Do these carbon cleaning systems like Terraclean actually work? Are they any better than some decent fuel and a trip to unrestricted German roads to get the engine properly hot?