Miami • Much to Audi’s chagrin, the A8 has been the best-kept secret in the luxury sedan segment. Fifteen years ago, long before Jaguar discovered the wonders of lighter-than-steel aluminum, Audi made its first light-bodied A8.

Well before Mercedes-Benz popularized the 4Matic option for its top-of-the-line S-Class, all of Audi’s flagship sedans ran quattro all-wheel drive. Yet, save for the possible exception of the thoroughly massaged and terribly hedonistic S8, Ingolstadt’s flagship sedan has made barely a dent in the marketplace.

Judging from the fanfare — Audi invited more than 1,000 autojournalists and guests to the Design Miami exposition to witness the unveiling — the company is finally abandoning its stealth marketing of the A8. It even constructed its own superstore-sized pavilion to unveil the slinky beast to all the fashionistas populating Design Miami.

What the Gucci-clad crowd saw was a four-door sedan more aggressive and much larger than the previous version. Longer (5,137 millimetres) and wider (1,949 mm) than its immediate competition, the new A8, says Audi, is lower for a more sporting silhouette. Add Audi’s now de rigueur LED headlights and tail lights, the company’s trademark, deep, shark mouth-like grille and you have one luxury sedan with significantly more attitude than its predecessor.

Said attitude is backed up with performance. Not only is the A8’s latest aluminum space frame torsionally stiffer than before, Audi says it’s also lighter. Factor in the increased output from the almost-ubiquitous 4.2-litre FSI V8 (now fortified with 372 horsepower) and the A8 scampers to 100 kilometres an hour in just 5.7 seconds, plenty quick for an all-wheel-drive sedan weighing roughly two tons.

But, it’s not the quickest in Audi’s A8 fleet. That honour rests with the 4.2 TDI engine, which, despite boasting a slightly less power (350 hp), pounds out a truly mesmerizing 590 pound-feet of torque — a whopping 262 more than the 4.2 FSI — and hits 100 km/h in just 5.5 seconds. A new eight-speed automatic transmission not only adds to its performance but also benefits the A8’s fuel economy.

Yes, for the first time in my recollection, a diesel-powered car is the sportiest version in a new model’s lineup. Audi further reinforces this impression by making the 4.2 TDI the only A8 that gets a limited-slip rear differential as standard equipment. Miraculously, Audi claims the 4.2 TDI only consumes 7.2 litres per 100 kilometres. Sadly, the big turbodiesel won’t be offered in North America.

As amazing as the 4.2 TDI’s fuel economy numbers are, they are outshone by the efficiency generated by a brace of 3.0L TDI V6s — which Audi will eventually offer in the A8. The first to be available (again, in Europe) will be a 250-hp unit. The more interesting of the duo is a 204-hp variant designed for maximum fuel economy, which, Audi boasts, is a piddling six litres per 100 km. Yes, it only features fuel-saving front-wheel-drive, but 47 freakin’ miles per gallon from a car only slightly smaller than the Queen Mary is astonishing.

Emphasizing that otherworldly performance is the A8’s incredible luxury. A camera-based system allows the A8 to auto-dim its LED headlights. The automatic climate control system can be had with four separate climate zones, Audi’s MMI on-board computer sees an upgrade and the normally 12-way-adjustable front seats can be swapped for a pair of 22-way chairs (and don’t ask me to list the 22 ways a seat can be adjusted). They’re ventilated as well as heated and can be had with a pneumatic massager.

The A8’s audio system also gets a boost, the optional Bang & Olufsen stereo now thumping out 1,400 watts and counting no less than 19 speakers, surely pushing the limit to what automobile windows and the human ear can endure — and making it likely the A8 will no longer remain the luxury sedan that nobody notices.

The new car arrives next spring.

dbooth@nationalpost.com