The Audi RS6 Avant isn’t just the most powerful estate the company has ever built; it is the most powerful car it has ever built for the road full stop. And that means it can out accelerate its big brother, the Audi R8 supercar.

So we sent Stuart Milne to Warwickshire to find out whether a supercar-baiting estate car is an intoxicating blend, or simply a niche too far.

As the assembled group of journalists Audi had invited to drive the new RS6 Avant, there was one question on everybody’s lips.

Is the Audi RS Avant the greatest estate car ever built?

On paper, it stakes a real claim to being just that. It develops 572bhp from its twin turbocharged 5-litre V10 engine. It can out-accelerate the Audi R8 supercar and can still carry a vast 1,660 litres-worth of luggage.

But cars can so often offer so much potential, and then fail to deliver.

And we’re pleased to report the Audi RS6 Avant is not one of them.

From the moment the engine burbles into life, it’s clear the new Audi RS6 Avant has performance and ability in spades.

Lamborghini engine

The V10 engine can trace its way back to the Lamborghini Gallardo, and is simply sensational. If it has a 21st century muscle car soundtrack at tickover, there’s full on heavy metal thunder when the engine picks up revs, making the hairs stand to attention on the back of the driver’s neck.

Audi only offers the RS6 with a six-speed tiptronic gearbox, which offers instant gearchanges, and allows the engine to emit a bark through the exhaust during full-throttle shifts; something that few petrolheads will tire of.

On the move, the Audi RS6 Avant feels staggeringly muscular, in a way only big-capacity engines can. It’ll reach 62mph from rest in 4.6 seconds, just a tenth behind the saloon version. The top speed for both models is an electronically-limited 155mph.

But at any speed, the RS6 picks up pace at an other-worldly rate, and feels considerably quicker than the Audi R8 supercar, regardless of what the two car’s figures may tell.

In fact, despite power being sent to all four wheels via Audi’s quattro system, it’s still possible to make the traction control light flash in both first and second gears.

Like all other hot Audis, the RS6’s quattro system means grip levels are staggering, and only the most talented drivers will be able to reach the car’s limits during cornering. And even then, only with the safety net of a track with big run-off areas.

There’s plenty of communication fed through the steering wheel, and the steering itself is very direct if lacking a little in weight.

Remarkably, the Audi RS6 Avant manages to feel much smaller than it actually is, enabling the driver to carve through bends in a manner more accustomed to a Subaru Impreza or Mitsubishi Lancer Evolution.

Ride quality is good for the most part, only bigger potholes upsetting the car when its Dynamic Ride Control system is in its comfort setting. Dial in extra firmness, and the RS6 begins to lose its composure.

But despite this, the seats are hugely comfortable, and would fit the bill for a long, high speed continental cruise.

View our Audi RS6 Avant slide show

Eleven miles per gallon

Of course, all this grip and grunt comes at a price. After forking out almost £80,000, you’ll need to factor in group 20 insurance every year, while emissions of 333g/km place it in the highest road tax bracket.

But the biggest concern is its thirst for fuel. Audi quotes an average fuel consumption of 20.2mpg, but our mixture of urban and fast-flowing country lanes yielded a little over 15mpg. But that was still better than the previous driver, who recorded around 11mpg.

Naturally space is excellent, with a vast 1,660 litre boot when the rear seats are folded – slightly more than the BMW M5 Touring, but less than the Mercedes E 63 AMG. There’s an underfloor storage area too, and a system which allows the opportunity to divide the boot to stop items sliding around.

Space inside is first rate, with rear head and leg room particularly impressive.

Standard equipment is what you’d expect from a £77,000 car, and includes 20-inch alloys, Dynamic Ride Control sports suspension, front and rear park sensors, adaptive xenon headlights, electric and dimming door mirrors, power tailgate and LED rear lights. Inside, occupants will find cruise control, front, front and rear side and curtain airbags, automatic wipers and headlights, electric front seat lumbar adjustment, front and rear seat heating and sports seats with nappa leather trim.

Entertainment wise, Bluetooth phone integration, BOSE stereo with digital tuner and MP3-compatible 6CD changer, hard disc-based sat-nav with 7-inch colour screen all some as standard.

On paper, it’s a case of bruised knuckles all round, with the Audi and its key rivals, the BMW M5 Touring and Mercedes E 63 AMG Estate. There’s very little in the 0-62mph drag, with the Audi, BMW and Merc posting 4.6, 4.7 and 4.5 seconds respectively. All are limited to 155mph.

So is the Audi RS6 Avant the greatest estate car ever built? Quite possibly, with its Lamborghini-derived V10 engine, scintillating performance and pumped-up, handsome looks. Just don’t mention the fuel economy.

Key facts

Model tested: Audi RS 6 Avant 5.2 TFSI quattro
On the road price: £77,730
Price range: £76,160 – £77,730
Date tested: October 2008.
Road tester: Stuart Milne