Audi S6 Avant TDI review: is this diesel wagon the ultimate family car?

I don’t care about the Audi S6 any more. I want the new RS6.

Don’t we all? But the S6 is now controversial and a bit different, and it makes odd noises. So give it your attention.

Controversial? Strange noises?

Yep. Audi’s morphed the S6 into a super-diesel – but needs to convince the S6 faithful, who are used to a diet of turbo V6 and V8 Q-cars – that the new S6 TDI is still a proper bit of kit.

So, it’s piped in a lot of artificial engine noise through the speakers. A real ‘grrrrrr-bwwwaaar’ sound, part flat-four Subaru, part big-capacity V8. You don’t expect that kind of silliness in an S6. S6s are serious cars for serious people who need to be very far away in not much time at all and would rather no-one really noticed them. This diesel-powered S6 is – despite its four exhaust pipes – probably the quietest S6 ever. And yet, inside, it’s going ‘grrrrrr-bwwwaaar’.

But you can turn off that, right?

You can. There, that’s better.

So, why a diesel for the S6 these days? That’s a bit… unfashionable.

Audi’s official answer, as we discovered when we tested the new V6 TDI S4, is that it still sees a big demand for diesel cars in Europe, and that diesel cars help get the company’s CO2 averages down where they need to be. This car emits 171g/km, officially. The old S6 had a woofly 4.0-litre V8, chucking out 219g/km, and that was on the old, much more flattering test cycle. You can see Audi’s logic.

Off the record, it pleases Audi Sport’s marketing bods. If you’re asking someone to shell out £90k for say, an RS6, it doesn’t look as appealing when the cheaper S-car has a same-size, same-sound engine. So, now the S6 is a V6 diesel, that new RS6 – which sticks with V8 petrol power – seems more special, straight out of the box.

Unless this diesel is brilliantly good. Is it?

It’s very impressive, but it doesn’t immediately grab you by the jowels and shout that in your face. You have to spend some time in the S6, live with it, in lots of weather with lots of people on board, before you start to appreciate how accomplished this car is.

Take the power. On paper, 344bhp and 516lb ft is certainly meaty, but hardly box office these days. Maximum torque is bigger than the old V8’s, but only lasts for 600rpm (from 2,500 to 3,100rpm). Audi claims a limited top speed of 155mph, and on the way you’ll pass 62mph in about five seconds. It’s brisk, sure, but it’s also a £60,000 Audi that’ll struggle to keep up with a Hyundai i30N. And some of the S6 faithful won’t be impressed by that. Not at first.

But after a while, the S6 starts to come good. The way it leaps out of roundabouts and peels onto sliproads is deeply appealing. It accrues speed and uses that morsel of mega-torque to great effect by shifting the eight-speed gearbox seamlessly to stay in the boost zone. No, it’s not an exciting powertrain to use, even though the motor makes an appealing rasp if you bother to rev it to 4,000rpm. It’s not an entertainer, but it’s a very willing ally. Spot a gap, squeeze the throttle, and no-one on board really notices that you’ve just added 15mph to your speed and overtaken that dawdling middle-lane hogger. It mugs people.

How economical is it?

Glad you asked, as the praise was starting to runaway like the S6’s momentum just there. Here’s the rub – this isn’t a very parsimonious diesel. Normally, diesels don’t take much concentration to pull great mileage. But the S6… well in normal driving, in its 80mph @ 2,000rpm motorway comfort zone, it’ll settle at 35mpg. As an average, it’ll do about 31mpg. If you’re really good and learn to coast plenty to let the 48-volt hybrid system shut the engine down and decouple the transmission, it might go higher still. But only briefly.

Still, the old S6 V8 claimed 30mpg, and would really go low 20s. This time, Audi claims 36mpg, and you’ll get within 3-4mpg of that.

Better yet, the S6 has a proper fuel tank. Despite needing to package AdBlue, it offers up a 63-litre tank. Optionally, you can spec a 73-litre tank. Say what you like about diesel, but one day these cars will all be gone for scrap and we’ll miss the days you’d climb aboard something this effortlessly rapid and see a 600-mile range on the dash. Bring on those hydrogen fuel cells, eh?

How’s the handling?

Nose-heavy, obviously, but this is at least a fast Audi that doesn’t have suspension made of glass and wheels fashioned from depleted uranium. Even though they’re a massive 21-inches in diameter. As ever, spec the air suspension, but leave it out of Dynamic mode. Body roll is pronounced but the car controls its movements well enough and it’s decently cushioned on back roads. It’s nicely neutral, but a bit of a two-tonne pudding. A BMW 5 Series Touring feels sharper. Same old.

Should I buy this, or just a regular A6 Avant with a big diesel engine?

Probably the latter, with our sensible hats on. And yet… it is a pretty effective device, the S6. It’s a car you have to ‘get’ though. If you respect pace that’s effortless, bodywork that doesn’t shout about much, and visiting a fuel station half as often as the old S6, this is one heck of a desirable car. A four-wheel drive Swiss Army knife. And if you’re plunging headlong into the comments asking WHY? then at least you’ve not long to wait for the RS6.

7/10

£60,750
2967cc diesel V6
344bhp, 516lb ft
0-62mph in 5.1sec, 155mph
35.8mpg, 171g/km
2020kg