Audi S6: S stands for sensational

The S6 Avant boasts a 4.0-litre twin-turbo direct-injection V8, quattro four-wheel drive with Audi's Sport differential and sports air suspension.

Audi's S6 Avant station wagon is crazy-fast

There is no doubt that Audi plays fast and loose with the letter S. It's all because of its line of RS supercars - they are hero cars for the marque, which is why Audi also offers a huge range of "S-line" options to make mainstream models look a bit like RS-cars, and a more focused range of 'S' models that give some of the go-faster flavour without going all the way.

It might all seem like a slightly cynical way to cash in on the cache of RS - except that so many of those RS cars are so extreme, which leaves a lot of room for S-cars to be pretty sensational as well.

The $159,600 S6 Avant is a case in point. Audi does very nice station wagons and this one is based on the A6. Except that being an S6, it boasts a 4.0-litre twin-turbo direct-injection V8, quattro four-wheel drive with Audi's Sport differential and sports air suspension.

Downsizing is the way forward for performance cars these days and believe it or not that's exactly what Audi has done with this car, because the old one was a V10. While it was still far cooler to have a 'V10' badge on the front guards, this new engine provides more performance (0-100km/h in 4.7 seconds) and much better fuel efficiency (9.7 litres per 100km). It's the same V8 that you'll find in the larger S8 or even the latest Bentley Continental, in different states of tune.

It can run on four cylinders to save fuel when maximum power is not required; I don't think it did that much during my week.

It also sounds sensational, with a deep rumble at middling speeds and a glorious rasp as the dual-clutch S tronic transmission swaps gears.

Fast Audis are all about characterful engines and incredible traction. They're not necessarily designed to dance around corners like BMW M or Mercedes-Benz AMG models: the S6 Avant has aloof steering despite Audi's adjustable Drive Select system, and it's not always easy to change the cornering line once you're committed. But the S6 has a different kind of cornering prowess: it rewards smooth driving and has the kind of quattro traction that allows you to apply all of the power, all of the time. That's pretty exciting in its own way, especially when you have the soundtrack to match (that's a howling exhaust rather than screeching tyres).

So the S6 shares its engine with a Bentley. Yes, I know Volkswagen owns Bentley rather than the other way around, but might I suggest there's a bit of British nouveau riche influence in the S6's cabin? Audi interiors are usually luxurious and exquisitely finished but just a bit dull. Or perhaps a bit too similar to other models in the range. Not so the S6.

It's recognisably a product of the four-ringed marque, but there are some striking touches that remind one of the German car's upper-class cousin. Things like the sparkly instrument panel and intricately quilted leather upholstery. In any other German car I'd be inclined to say it's a bit over the top, in this case I'm just delighted Audi seems to be having some fun.

Well, fun in addition to making a big station wagon that's crazy-fast and completely unflappable. This car's performance and traction are surreal; the forthcoming RS6 is going to be quite a piece of work.

THE BOTTOM LINE

Mighty heart and manic cornering ability: the S6 is far from a poor cousin to Audi's RS models.