Surprisingly likeable. Despite its four-cylinder configuration the Audi’s diesel engine is relatively quiet on cold start-up and becomes even less audible as it warms. Compared to Mercedes’ 2.1-litre diesel it’s much more refined, and those who commute long distances will appreciate its smoothness.
It's hardly lacking in punch either, with the diesel's 187bhp and 292lb ft proving more than capable of accelerating the A6 with suitable – and occasionally surprising – verve. The new S tronic transmission rifles through the available ratios in a smooth, swift fashion too. In fact the only real gripe with the ultra's powertrain is an occasional hesitancy off the line but once it's moving progress is swift.
The Audi impresses elsewhere on the road. It's easy to manoeuvre, despite its substantial size, while good visibility and standard-fit parking sensors means slotting into a space isn't a chore.
Braking performance is more than adequate, with plenty of bite and an easily modulated pedal, although stopping in low-speed traffic can occasionally cause the A6 to lurch slightly as it assumes a parked position.
As you might expect, however, the Audi's dynamic qualities could do with a little improvement. Occasionally the A6's steering – which lacks the tactile feedback of a 5-series' – feels like it has too large a deadzone, so requires excess lock for what should otherwise be minor steering inputs.
It remains precise and responsive enough to avoid becoming an annoyance, though, and its weighting is ideal for those who just want an effortless drive from A to B.
The Audi's ride quality may irk some, as it borders on the overly firm and has a tendency to thud over cracks and through potholes, but the tradeoff is reduced body movement in high speed corners.
Opting for the more softly sprung and smaller-wheeled SE variant may bring back some of the pliancy that would be better suited to a car of its class. Nevertheless, in short, the Audi A6 ultra is an easy and hassle-free car to drive in either specification.
There are also hidden depths to the car's suitability as a business saloon. For example it has a large 73-litre fuel tank, granting it a potential range of 1030 miles.
That's similar to BMW's 5-series 520d. Mercedes' E-class E220 CDI, on the other hand, has just a 59-litre tank, resulting in a maximum range of around 800 miles.
Of course it's difficult to imagine that you'll ever get the Audi to hit that 1000-mile mark – but it's not unreasonable to expect it to return around or in excess of 50mpg, granting a long-legged 800-mile range.
Elsewhere, it's the same as the standard A6. The cabin is beautifully designed and that materials used throughout feel of a good quality, while four adults can be accommodated in comfort with ease. A fifth can sit in the central rear position but will have to straddle the A6's central tunnel and suffer reduced headroom.
On-road refinement is good – although road noise does intrude on some surfaces – and the A6's vast battery of standard kit works to reduce both driver strain and boredom. It's quick and easy to establish a Bluetooth connection and the Audi's media and navigation systems work well, although as always it's worth checking that the sat-nav's suggested route resembles a sensible approximation of your desired journey.
The Audi offers up a large boot as well and many buyers will appreciate the fitment of a standard space-saver spare wheel.