Apparently downsizing has now become upscale -- at least in the United States. Both long- and regular-wheelbase versions of Audi's A8 flagship sedan have historically been powered by V8 or W12 engines, but the base 2013 Audi A8 is propelled by a V6, and the results might surprise you.

The natural assumption leads most to think a V6 wouldn't be a good match with this big sedan's size and weight -- certainly not as good as a V8, in any case. Generating 333 horsepower, the new supercharged 3.0-liter V6 is down 39 hp and 3 pound-feet of torque compared to the previous 4.2-liter V8. We expected the V6 car to be marginally slower as a result, but it's actually marginally quicker than the heavier V8-equipped sedan. Meanwhile, the supercharged V6 car's fuel economy is essentially identical to that of the normally aspirated V8.

For these reasons, we doubt anyone would miss the former V8, especially since Audi has added a new and even more powerful turbocharged V8 to the A8 lineup. Later in the year, a diesel-fueled V6 will debut. Meanwhile, the 6.3-liter W12 remains the same as before, the perfect choice for those who think too much is just enough.

Engines aside, the 2013 Audi A8 maintains its place in the top tier of luxury sedans. It delivers a very high level of old-world luxury and comfort, along with a healthy dose of high-tech features that should delight any early adopter. This big Audi also manages to balance performance and luxury in a way that should appeal to drivers of all stripes. And for those who desire more emphasis on the performance side of the full-size sedan proposition, there's also an Audi S8, which is covered in a separate review.

Like its rivals, the A8 features an artful blend of understated styling, excellent craftsmanship, and exemplary interior materials. Picking a winner among them isn't easy, but then again, there's not a loser in the bunch. The BMW 7 Series and Mercedes-Benz S-Class mostly place an emphasis on luxury, while the Jaguar XJ and Porsche Panamera have more sporting demeanors. Those looking for a middle ground would do well to try out the 2013 Audi A8.

The 2013 Audi A8 "Quattro" is an all-wheel-drive luxury sedan that is offered in regular- and long-wheelbase versions, the latter described by "L" and bestowed with about 5 extra inches of rear legroom. Trim levels include 3.0T, L 3.0T, 4.0T, L 4.0T and L W12. Each designation corresponds to the wheelbase and engine types.

Standard features for the base 3.0T include the new supercharged V6 engine, 19-inch alloy wheels, adaptive xenon headlights, LED running lights, headlight washers, a sunroof, adaptive air suspension, dual-zone automatic climate control, auto-dimming and power-folding mirrors, heated 12-way adjustable front seats with driver memory, a power tilt-and-telescoping steering wheel, aluminum and wood interior trim and a power rear sunshade. Electronic features include a navigation system, Audi's MMI electronics interface with voice control, Bluetooth phone and audio connectivity and a Bose surround-sound system with a CD player and an iPod interface. Also included is Audi Connect (enhanced Web-based navigation, information and WiFi access).

While the A8 3.0T is well equipped, there are a number of available options. Buyers can add the Convenience package, which includes a power trunk lid, keyless ignition/entry, parking sensors with rear- and top-view cameras, and soft-close power doors. An Extended Leather package wraps the armrests, center console and steering wheel airbag cap in leather. The Warm Weather package adds four-zone automatic climate control and power rear window sunshades.

Opting for the long-wheelbase L 3.0T version includes the above three packages in addition to piano-black interior inlays.

To either wheelbase, 3.0T buyers may choose to add a Cold Weather package consisting of a heated steering wheel, a ski bag for the rear seat pass-through and heated rear seats. A Comfort package includes 22-way multicontour comfort front seats with ventilation and pneumatic massage, plus wood inlays on the front seatbacks. The Sport Design package includes the Comfort package items but adds 20-inch wheels and upgraded leather upholstery. For a sportier A8, the Sport Plus package applies summer tires, a sport-tuned suspension, adaptive steering and a sport differential. Finally, the Driver Assistance package includes adaptive cruise control with automatic pre-braking and stop-and-go functionality, a blind-spot monitor and a lane-departure warning system.

Stand-alone options include full LED headlights/turn signals, a panoramic sunroof (L 3.0T), a solar sunroof (powers a ventilation fan to keep the car cool), dual-pane acoustic windows, a premium Bang & Olufsen sound system, a night vision camera (an infrared camera to detect animals and pedestrians up to 1,000 feet away), a rear-seat entertainment system (with two 10-inch headrest-mounted screens) and a choice of several headliners and interior trim elements.

The 4.0T and L 4.0T models are pretty much offered with the same optional equipment as the 3.0T models.

Previously available only on the top-shelf L W12 but now available on the L 4.0T is the Executive Rear Seat Comfort package. It includes powered control of the front passenger seat from the rear seat (and reduces the front seat to 10-way power adjustment without massage), the Rear Seat Entertainment package plus heated and ventilated rear seats, a fixed rear center console with its own MMI controller, a reclining rear passenger seat with power footrest, multi-program massage with remote and a small refrigerator in the rear center pass-through. Twenty-inch wheels are a stand-alone option.

The prestige-level L W12 is essentially a fully loaded four-seat long-wheelbase model that is powered by a 12-cylinder engine and includes almost all of the above listed features and many of the options, rolling on 20-inch wheels. Still optional, however, are the Driver Assistance package, W12 Sport package, Executive Rear Seat package, Audi Design Selection package, Bang & Olufsen sound system, night vision camera and solar sunroof.

Powering the base model 2013 Audi A8 is a supercharged 3.0-liter V6 that produces 333 hp and 325 lb-ft of torque. All of this power is channeled through an eight-speed automatic transmission and all-wheel drive. In Edmunds testing, a long-wheelbase L 3.0T with the optional Sport Plus package accelerated from zero to 60 mph in 5.3 seconds, which is quicker than every V6-powered competitor and just off the pace of those packing V8s.

Also standard on the V6 is an automatic stop/start feature that shuts the engine off when the car comes to a stop. It helps to increase fuel economy, which is quite good for this class of car at an EPA-estimated 18 mpg city/28 mpg highway and 21 mpg in combined driving for either wheelbase.

The new turbocharged 4.0-liter V8 produces 420 hp and 444 lb-ft of torque. Stop-start, an eight-speed transmission and all-wheel drive are also standard. In Edmunds testing, an A8 L 4.0T ran to 60 mph in just 4.2 seconds. The EPA estimates the 4.0T should earn 17 mpg city/28 mpg highway and 21 mpg combined, or nearly the same as the supercharged V6. The L 4.0T is only slightly more thirsty at 16/26/19 mpg.

Audi A8s with the 6.3-liter W12 engine only come in long-wheelbase configuration but benefit from 500 hp and 463 lb-ft of torque. As with all A8s, an eight-speed automatic and all-wheel drive are standard. Weighing in about 200 pounds more than the L 4.0T, Audi claims the L W12 will reach 60 mph in a scant 4.4 seconds. The EPA estimates fuel economy at 13/21/16 mpg.

Details regarding the new turbodiesel V6 are forthcoming.

Standard safety equipment for every 2013 Audi A8 includes antilock brakes, stability and traction control, full-length side curtain airbags, front- and rear-seat side airbags and active front headrests. The optional Driver Assistance package also includes a blind spot monitor and lane-departure warning system, as well as Audi Pre-Sense Plus, which monitors traffic and alerts the driver if a potential collision is detected, even applying the brakes (to a standstill below 20 mph).

In Edmunds brake testing of a V6-powered A8 with the optional summer tires included with the Sport Plus package, the car came to a stop from 60 mph in an impressively short 104 feet. All-season tires delivered a stop of 121 feet, which is average for similarly equipped cars in the class. An A8 L 4.0T with all-season tires came to a stop from 60 mph in 114 feet.

When we heard that a supercharged V6 would replace the base V8, the news was met with quite a bit of skepticism. As it turns out, the new V6 is actually quicker to 60 mph, if only by a few tenths of a second. We contend that few drivers would ever suspect the difference between the two engines.

Power is plentiful, whether under acceleration or cruising down the highway. Passing slower cars is effortless and the brakes are equally up to the task of bringing the big sedan to a halt. The even newer 4.0T power plant is even more impressive. While earning nearly the same fuel economy as the supercharged V6, the turbo V8 delivers a tidal wave of effortless torque. If you're so inclined, it will also go toe to toe with almost any muscle car in a drag race.

With its all-wheel drive, automatic air suspension and crisp steering response, the A8, in either wheelbase configuration, handles like a smaller, lighter sport sedan. Yet over broken pavement the Audi flagship delivers a compliant, composed ride fully in keeping with its luxury sedan status. We also like its electronically adjustable settings for the chassis and engine calibration, which provide a much greater degree of driver customization than BMW's similar system.

All things considered, the 2013 Audi A8 is a worthy competitor among world-class luxury sedans. While the gap between its rivals is narrow, the Audi does distinguish itself by being more of a "driver's" car, rather than being an isolation chamber.

As Audi's flagship, the 2013 A8 represents the best that the company has to offer. With the best materials combined with impeccable craftsmanship, the cabin is one of the finest in any flagship luxury sedan.

As you'd expect, comfort is a priority and the A8 delivers it in heaping portions. The upgraded seats found in the Comfort package adjust in so many ways that Audi needed to invent a more advanced means of controlling them, and they ultimately ensure that drivers of any size or shape will find an optimal position to motor away countless miles. Rear-seat comfort is also noteworthy, especially in the long-wheelbase versions that provide an expansive 43 inches of rear legroom.

For technophiles, Audi's Multi Media Interface provides a long list of functions through a crystal-clear display. There's a bit of a learning curve to it, but with a little time, control of numerous systems becomes second nature. The unique remote touchpad (upon which you can "write" numbers and letters with your finger) also doubles as a radio preset panel. It may seem like a superfluous novelty at first, but it turns out to be as useful as it is cool.

If there's one complaint that seems to come up more than others, it would be the A8's lack of trunk space. At a paltry 13.2 cubic feet, cargo capacity is far below that of its competitors and not nearly adequate to accommodate luggage for four adults.