Full-size luxury doesn't come without a cost--in price, or in weight. So while the Audi A8 weighs between 4,400 and 4,800 pounds, it's one of the lighter vehicles in the super segment it calls home. As with the Jaguar XJ, the A8's heavy use of aluminum lightens and brightens its entire performance, endowing it with assertive handling and relatively great gas mileage, and absolutely great fuel economy with its new turbodiesel engine.
Last year, Audi turned in the A8's old V-8 powertrain and adopted three new ones--or two, depending on how we'll count them. The group of four included a new supercharged six, a twin-turbo V-8 tuned to two different power outputs, and the carryover W-12 engine. This year, to make things very interesting, the A8 gains a 3.0-liter turbodiesel six-cylinder that posts major EPA highway numbers without too great a sacrifice on the stopwatch.
All the variants of the A8 have their own mission, and picking a favorite is simpler than it seems. If you're seeking entry into the segment and need to keep things on the spare end of the spectrum, the A8 3.0T is the choice you'll make. It's available in either wheelbase, both powered by Audi's supercharged 3.0-liter V-6. Output settles in at 333 horsepower and 325 pound-feet of torque, and it's coupled to an eight-speed automatic and quattro all-wheel drive, both of which are standard on all A8 variants. It's not as free of vibration as the V-8 was, and when it gets vocal it's unmistakably a V-6, but it's fast and responsive to inputs, the net of the low-end torque of the supercharger and the very well spaced gears of the paddle-shifted ZF eight-speed. Zero to 60 mph times of 5.5 seconds and a top end of 130 mph are respectable numbers at a respectable price point.
Next up is the brand-new turbodiesel in the A8 L TDI. Also a 3.0-liter V-6 unit, it posts the usual low diesel horsepower numbers and the gobstopping torque figures--in this case, 240 hp and 406 pound-feet of torque. With tires optimized to goose fuel economy, the TDI's estimated at 6.4 seconds in the 0-60 mph sprint, but doesn't dissolve into a heap of sluggishness by adding that nine-tenths of a second. If anything, the diesel's fantastic driving range of more than 800 miles on a tank absolves it of the drivetrain and tire noise that's lightly layered into the cabin on acceleration. The 36-mpg EPA highway rating is easily attainable, too--we nailed it in 80-mph jaunts over an 800-mile weekend, without much effort or thought.
Those fuel-conscious alternatives aside, the other A8 models power ahead with more cylinders and far more horsepower. Audi's new 4.0-liter twin-turbo V-8 pulses with an altogether more visceral brand of power than either the gas or turbodiesel six. In standard issue, it has 420 hp and 444 lb-ft of torque, and slices 0-60 mph times to 4.7 seconds. Which is fine until you consider the same engine in a more advanced state of tune turns in 520 hp in the Audi S8, and delivers 60 mph in 3.9 seconds along with a top speed of 155 mph. The former comes in either body style, the latter only as a short-wheelbase sedan. No matter which you choose, disappointment isn't an option.
At the ne plus ultra end of the A8 lineup, there's the unusual flagship engine, a W-12 of 6.3 liters and 500 horsepower. Those unconventionally arranged cylinders develop 488 pound-feet of torque, and shove the A8 L to 60 mph in 4.4 seconds, and to a 130-mph top end. We've driven this powertrain more in other VW Group products than we have in the A8, and frankly, given the configuration options and performance of other versions, we'd probably opt for one of the other entries anyway.
No matter the power source, every A8 shares the same eight-speed automatic--and Audi simply nailed its calibration. It always seems to grab the right gear quickly, and simply, and smoothly. It's also one of the reasons the A8 scores such impressive fuel economy numbers (up to 29 mpg highway with the 3.0T). If you're in its Comfort or Auto modes, the transmission shifts early; if you press intently, it's happy to fire off multiple downshifts before you can click the steering-wheel-mounted shift paddles. Even in the six-cylinder long-wheelbase models, an eighth-to-third downshift brings about a rush of meaty passing power.
Quattro all-wheel drive delivers sure-footed feel to the A8, even though the complexity of its suspension and wheel-and-tire offerings require a patient hand and Microsoft Excel license. (It's a German thing.) Quattro splits torque front to rear at a 40:60 ratio from takeoff, shifting power to a maximum of 60 percent front if the myriad sensors determine it need be so. On the S8, an active torque split from side to side comes into effect with the sport differential; it's now an option on other models as part of a Sport plus package, along with dynamic steering, adaptive air suspension, and summer 265/40 tires.
And therein lies the complexity. It's possible to configure an A8 3.0T with 19-inch all-season tires, or to opt an A8 L W12 up to Sport plus with summer tires, or to crank up the S8 to 21-inchers. The spectrum is broader than you think, particularly with Audi's Drive Select system on tap.
Drive Select is the electronic godhead that controls the A8's powertrain responses, steering weight, and suspension feel. It's set up with Comfort, Auto, Dynamic, and Individual modes, the last one of which can be programmed by the driver. It's a system that's gotten better in its current iteration, as Audi's switched over to electric power steering; the rack itself doesn't have much feel, but the disparate sensations across the systems in older Audis has been overcome, and Drive Select gives a more coordinated set of responses between throttle, ride, and shifts.
Maybe there's a little too much heft dialed into Dynamic mode, but that choice exists for the few enthusiasts who'd choose this model over an A7. But in all, the A8 is nicely tuned. There's barely any lift under hard acceleration or nosedive under hard braking—adding to the sophisticated, composed feel of the A8.
Of course, you can play tantric games with Drive Select too--put the S8 into Efficiency mode, or dial the W12 into Dynamic--but like real tantric moves, it's more enjoyable in theory.
The high-water mark of the group is set by the S8, of course. It's not a pure athlete, not at 4,500 pounds, but compared to some of its rivals, it feels like a sprinter. It's still blessed with enough body lean and ride compliance to feel less like an outlier in the A8 family--but also, to feel completely natural charging out of an exit ramp at triple-digit speeds, utterly composed thanks to variable-ratio steering and outstanding brakes.