In terms of depreciation, there’s barely any daylight between the three cars although none is particularly impressive, with the Audi tipped to retain a residual value of 41% after three years and 36,000 miles, the Mercedes 43% and the BMW 42%. The petrol-engined A7 55 TFSI does marginally better than its diesel sibling, at 43%, although its list price is £1100 higher.
Fuelling from the green pump will cost you an extra 10mpg in official combined figures, too, the TFSI managing 40.4mpg to the TDI’s 50.4mpg.
The A7 also comes well equipped: electric leather seats, LED headlights, 19in wheels, parking sensors and cruise control are included in Sport trim along with smartphone mirroring for both Apple and Android devices and the lowest CO2 emission figures in the range – 147g/km with the 45 TDI and 50 TDI engines.
Upgrading to S line gets you more aggressive exterior styling, 20in wheels, adaptive LED lights and lowered sports suspension. CO2 also rises to 150g/km.