Audi broke new ground back in 1994 with the original A8, whose all-aluminium body was a breakthrough in the saloon segment. The second-generation A8, launched almost 10 years later in 2003, continued to use the innovative ASF (Audi Space Frame) but was no longer alone in its aluminium niche.
Jaguar had introduced its old-look but new-tech XJ made of the same metal, and Rolls-Royce under BMW rolled out the Phantom around the same time, with an aluminium spaceframe chassis clad in aluminium body panels. The Coupe and Drophead derivatives of the Phantom, along with the radical new “Tata” XJ, are also aluminium cars.
The third-generation A8 is again an object lesson in automotive aluminium, but it has added steel to the equation for the first time. Used for the B-pillars, ostensibly for superior stiffness and better side impact protection, the steel has to be specially attached to the aluminium structure with flow drill screws – a new manufacturing technique.
The A8 bodyshell sports 632 such screws, along with 1847 self-piercing rivets, 202 welding points, 25 metres of MIG-welded seams, six metres of laser-welded seams and 44 metres of bonded seams.
A more interesting set of numbers is provided by the weight savings, which go beyond the well-known aluminium advantage. The A8’s bare body weighs 231kg, roughly 40 percent less than an equivalent steel body, and yet registers a 20 percent increase in torsional rigidity against the previous A8.
The end result is a fully equipped 4.2-litre V8 A8 that tips the scales at just over 1.8 tonnes. This is some 200kg lighter than a BMW 750Li, and all the more impressive considering the new A8’s extensive luxury equipment and extremely sophisticated vehicular systems. 
Read our review of the Rolls-Royce Phantom II, an aluminium limousine.
Read our review of the 2-litre Jaguar XJ, another aluminium limousine.
