Used car buying guide: Audi S6
16 August 2021 - autocar
This hot A6 is an underrated executive car that’s shaded by its RS-badged rangemates, but it’s not without its issues
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 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.
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.
No S6 owner went without. Standard kit includes 19in alloy wheels, bi-xenon headlights that track corners, leather seats and tinted glass. Among the plethora of options available were carbonfibre interior trim, larger 20in wheels, a rear blind and an uprated sound system. Today, though, the best option is a full service history. Many S6 sellers claim their car has one, but reserve judgement until you’ve checked every last stamp and invoice.
How to get one in your garage
An expert’s view
Martin Adams, Founder and Director, Unit 20
“The S6 is a very good car that suffered in the shadow of the RS6. Its 5.2-litre V10 is erroneously linked to the dry-sump V10s in the RS6 and Lamborghini Gallardo, but it shares little with them. It’s reliable but parts are expensive, meaning the ‘cheap’ S6 you find may not be so cheap to own. There are 10 spark plugs, 10 coil packs and 10 injectors, and the plugs alone cost £240. Each front brake disc costs around the same. Rust isn’t an issue but serious dings and dents can be expensive to sort. Interiors are robust and reliable but these cars are now up to 15 years old, so the tech is dated.”
Engine: Oil services are every 10,000 miles or 12 months. Valves are prone to carbon fouling that can only be fully eradicated with expensive dismantling. The four timing chains are at the back of the engine, making removal and replacement very expensive. The chains are reliable but the plastic guides and tensioners can fail. Injector problems are common on older cars and replacing all 10 isn’t cheap. On the test drive, feel for running issues at speed – the variable-length manifolds have a tendency to break up inside.
Exhaust: Horribly complex system is expensive to put right when it fails. Flexi-joints suffer leaks caused by corrosion.
Transmission: It’s sealed for life but specialists recommend changing fluid and filter every 40,000 miles.
Brakes, suspension and tyres: Alloy suspension parts are durable but bushes will be tired by now. Replacing them will be transformative. Brake parts are expensive so beware lipped discs and worn pads. Mixed, nonpremium tyres suggest servicing and maintenance have been skimped.
Body: S6s only rust when badly repaired. Check for overspray under window rubbers and for mismatched fixings on the bonnet slam panel and wings. Shutlines should be millimetre perfect. Feel for damp under the boot carpet and check the boot floor for repairs.
Interior: S6s hide mileage well so check that the condition of pedals and steering wheel match the car’s mileage.
Also worth knowing
A used S6 that has been properly serviced should present few problems, but you might want to consider an extended warranty. Audi’s 12-month all-component cover with a £250 excess and an annual limit of 10k miles is £2186. It’s pricey but comprehensive.
How much to spend
£7000-£8499: Private-sale saloons with lots of miles and multiple former keepers, but a few good bargains nevertheless.
£8500-£10,999: Nicer cars, like a private 2006 saloon with 96k miles and FSH for £8995.
£11,000-£12,999: Later, well-equipped cars from ’09-on with 100k miles or so and in good nick.
£13,000-£14,999: Best cars here with around 80,000 miles and solid histories. Includes a 2008-reg saloon with 81,000 miles and a full Audi service history.
One we found
Audi S6 5.2 V10 Quattro, 2008, 130,000 miles, £7999
This tidy, unmolested car has a fully stamped service history, but we’d want to check the invoices for work done. It has had a recent intake Terraclean to rid its valves of carbon deposits.