The 520d is punchy enough for most people and is our pick of the range. If you don't believe us, check out its claimed 0-62mph time of just 7.2 seconds, which is plenty for whisking you up to motorway speeds without any fuss. Performance is roughly on a par with the rival Mercedes E220d, although in terms of real-world drivability (as opposed to outright 0-62mph acceleration), the Audi A6 40 TDI has a slightly wider performance window, and is fractionally more flexible as a result.