Audi A6 3.0 BiTDI

The Audi A6 and BMW 5 Series have been locked in battle for years. The latest generations of both have held Auto Express Best Executive Car titles and are the benchmark the new Lexus must face up to.

Worryingly for the GS 450h, though, the latest addition to Audi’s armoury is a potent diesel engine which is designed to offer class-leading performance. The new BiTDI is the most powerful V6 TDI yet, pumping out 309bhp and a whopping 650Nm of torque. We’ve tested the car in S line trim, and its sporty styling cues subtly enhance the A6’s slightly uniform and bland looks.

Still, if the exterior leaves you cold, the interior is sure to win you over. Beautifully clear yet upmarket instruments blend with Audi’s intuitive MMI control system and a perfect driving position to create a very functional and comfortable cabin.

The quality is faultless, while classy trim and swish design ensure it’s luxurious without being ostentatious. Standard kit is generous and the navigation screen gracefully slides out from the dash.

However, the real star of the show comes to life when you press the centre console-mounted start button. The 3.0-litre TDI engine hums gently at idle and is really smooth throughout the rev range, while the effortlessly rapid performance is nothing short of sensational. Quattro all-wheel-drive traction helps the A6 cover 0-60mph in only 5.6 seconds – but it’s real-world muscle that counts here, and the Audi doesn’t disappoint.

The eight-speed Tiptronic gearbox takes a while to react when you press the throttle at low speeds, yet with all that torque the engine doesn’t take long to get into its stride. And while the 535d is fractionally quicker in-gear, nobody will feel short-changed by the BiTDI’s performance, especially as the engine sounds so good. It’s as refined as you’d expect, but Audi has fitted a clever sound actuator in the tailpipe that artificially creates a sporty petrol-like exhaust note. Clever stuff.

The good news continues in corners, where the tightly controlled body roll and huge grip really impress and help this big saloon to feel smaller and more agile than its rivals. Also, Audi’s Drive Select system allows for fine-tuning of the chassis, although the differences between modes are subtle.

With a 20mm lower ride height and optional 20-inch wheels, our S line test car didn’t ride as well as the BMW, but the accurate steering, composed handling and scintillating performance ensure this is a diesel saloon to enjoy on a back road.

Unfortunately, despite stop-start the A6 has the highest emissions in the test – something that could deter company car drivers looking to minimise their tax bills. Could that be enough to cost this very desirable Audi victory in such a closely fought battle?

Details

Chart position: 2Why? We are big fans of the latest A6, and the new bi-turbo 3.0-litre TDI engine gives it even more punch and desirability. We test the car in sporty S line trim.