Great green appeal, but a BMW 520d is just as green and a better drive.

What is it?

The greenest version of Audi’s revised A6 range, which improves fuel economy, trims CO2 emissions and – most usefully – reduces company car tax liability.

Design tweaks have been subtle but well thought-out, both outside and inside. The MMI control system has been revised to be more instinctive to use and the satnav system has been upgraded. But the really important changes to the 2.0 TDIe are mechanical.

The old 2.0-litre ‘pump duse’ TDI engine has been pensioned off, and Volkswagen’s new common rail diesel engine introduced. To make the most of every last drop of diesel, taller gear ratios have been fitted, and now the power steering pump only operates on demand.

Similarly the alternator engages to claim energy that would otherwise be lost while coasting, and the TDIe’s ride height has been dropped by 20mm so the A6 will slip through the air more easily.

What’s it like?

Impressively economical, at least in isolation. Audi claims 53.3mpg on the official combined cycle, with the TDIe only available with a six-speed manual transmission. Carbon dioxide emissions of 139g/km are also good enough to give a rock-bottom company car tax band for a diesel.

Efforts to improve refinement haven’t been quite so successful. Hard acceleration brings too much noise for comfort while getting up to speed. Performance is brisk enough, provided you ignore the dashboard display which tries to persuade you to change into sixth at the earliest opportunity.

The TDIe is only available with steel springs, unlike most other A6s, which can be specified with air suspension. That’s a shame, as the TDIe doesn’t ride as well as air-sprung versions.

It’s a little too firm for comfort, and can be slow to recover its composure over sharp bumps at speed. You can hear the suspension working rather more than you’d expect, too.

Otherwise the A6 TDIe is a pleasant car to drive and travel in. There’s plenty of grip, in spite of relatively narrow 205/60 rubber, and light but precise steering. Cabin quality continues to set the standard by which rivals are judged.

Should I buy one?

As much as we admire the TDIe’s green credentials, it isn’t moving the game on. Indeed, the BMW 520d manages to combine more power with lower economy and emissions figures, and as the clean, green exec it remains the first choice.

David Motton

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ThwartedEfforts 24 September 2008

Re: Audi A6 2.0 TDIe

Autocar wrote:

It’s a little too firm for comfort, and can be slow to recover its composure over sharp bumps at speed.

Sadly, the world's most atrocious ride quality is something Audi will never address while idiots are buying them in record numbers. It's like asking Whitney Houston to stop warbling.

Anyway, doesn't Vorsprung durch technik mean 'sprung without technology'? :)