All versions of the A8 get an eight-speed automatic gearbox and Audi’s quattro four-wheel drive system as standard. The most popular engine by far is the 3.0-litre V6 diesel, which is also our pick of the range. That's partly because it’s the cheapest option but feels anything but cheap, being powerful, smooth and with enough straight-line pace to surprise much sportier cars.
There’s also a 4.2 V8 diesel, which is fantastic to drive but a bit pricey next to the 3.0-litre V6. In fact, much the same could be said of the ludicrously rapid S8 and S8 Plus models, which use a heroically powerful 4.0-litre bi-turbo V8, while the 6.3-litre W12 is really for those with more money than sense, sublime as it is.
You can also get the A8 in short and long-wheelbase models, the latter being available with every engine apart from the S8’s V8, while the W12 is long-wheelbase only.
A classy-looking dash, smart infotainment system and lavishly comfortable interior all count in the A8’s favour, but it doesn’t offer quite as much rear passenger space as those other rivals. You also get a better ride comfort, and more advanced safety features on the Mercedes and BMW than on the Audi A8.
Predictably, being a much older model than the Mercedes or BMW, the Audi A8 is the cheapest of these big limos on list price, and is also routinely offered with huge discounts. CO2 emissions lag behind the class best a bit, so company car drivers will likely find more appeal and value in the A8’s rivals.