Overcoming a challenge can sometimes push you to higher levels of achievement, and such is the case with the 2013 BMW M5. One of BMW's goals has been to make this model more fuel-efficient for our greener times. Mission accomplished, and in the process, BMW has somehow managed to enhancethe M5's athletic personality.

At the heart of the M5's successful evolution is its new engine. Gone is the previous generation's normally aspirated and high-revving 5.0-liter V10; in its place is an updated version of the twin-turbo 4.4-liter V8 used in other M products such as the X5 M. Compared to the previous V10, output has increased from 500 to 560 horsepower and torque has leapfrogged from 383 to 501 pound-feet. The end result is a car that launches like a cannon shell out of the hole, yet overall fuel economy is 30 percent better, BMW claims.

Paired with this new power plant is BMW's seven-speeddual-clutch automated manual transmission (DCT). Smooth and responsive, this gearbox is a vast improvement over the clunky single-clutch SMG setup seen in the outgoing model. Hard-core BMW enthusiasts in North America will also be pleased to see that one can still purchase the M5 with a six-speed manual transmission; for everywhere else in the world, the M5 comes with the DCT only.

Naturally, there are M division changes to go with all this new hardware. Compared to the regular 5 Series, BMW has added more powerful brakes plus various measures to stiffen the chassis. Out back, there's a new electronically controlled limited-slip rear differential. The 2013 BMW M5 also looks the part with a deeper front chin spoiler, larger air intakes, chrome-trimmed vents in the front fenders, a subtle rear spoiler and sizable quad exhaust pipes.

With choices like the Cadillac CTS-V, Jaguar XFR, Mercedes-Benz E63 AMG and Porsche Panamera, this segment of high-performance, high-dollar cars is rich with superb alternatives. Yet with the M5, BMW has managed to combine refinement and livability with pleasures of the most visceral persuasion. It's a blend that should prove irresistible to well-heeled enthusiasts.

The 2013 BMW M5 is a high-performance variant of the midsize 5 Series luxury sedan. Standard equipment includes 19-inch alloy wheels, performance tires, adaptive suspension dampers, adaptive xenon headlamps, an automatic start/stop function, front and rear parking sensors, auto-dimming mirrors, a sunroof, dual-zone automatic climate control, a power tilt-and-telescoping steering column, leather upholstery, 16-way power sport front seats, heated front seats with memory settings, and split-folding rear seats. Standard electronics features include the iDrive electronics interface, a navigation system, voice commands, a rearview camera, Bluetooth and a 12-speaker surround-sound system with a six-CD changer, HD radio, an auxiliary audio jack and an iPod/USB interface.

The optional Driver Assistance package adds lane-departure and blind-spot warning systems, along with side- and top-view cameras. An Executive package adds keyless ignition/entry, a power-operated trunk lid, soft-close doors, a heated steering wheel, ventilated and massaging functionality for the front seats, four-zone automatic climate control, heated rear seats, a power rear sunshade, manual rear side window shades, a head-up display, satellite radio and smartphone app integration. Stand-alone options include 20-inch wheels, carbon-ceramic brakes, a rear-seat entertainment system, a 12-speaker Bang & Olufsen surround-sound system and a night vision camera system with pedestrian detection.

Motivating the rear-wheel-drive 2013 BMW M5 is a twin-turbo 4.4-liter V8 that generates 560 hp and 501 lb-ft of torque. This power is directed by a seven-speed, dual-clutch automated manual transmission (DCT). A six-speed manual transmission is offered as a no-cost option. According to BMW, the M5 should accelerate from zero to 60 mph in 4.2 seconds with the DCT; a manual-equipped car is said to be a hair slower at 4.3 seconds.

Standard safety equipment for the 2013 BMW M5 includes stability and traction control, antilock disc brakes, front-seat side airbags, active front head restraints and the BMW Assist emergency communications system. The stability control system includes a feature designed to improve braking performance: Brake rotors are periodically wiped dry in wet conditions and brake pads are automatically snugged to the rotors when the driver abruptly lifts off the throttle.

Optional safety equipment includes a lane-departure warning system, a blind-spot monitor and a night-vision system capable of displaying oncoming animals, objects or people that are beyond the range of the car's headlights.

The 2013 M5 hasn't yet been crash tested, but the structurally similar 2012 5 Series scored a top five-star rating for overall performance in government tests, earning four out of five stars for overall front-impact protection and five stars for overall side-impact protection. In Insurance Institute for Highway Safety testing, the 5 Series earned a top rating of "Good" in the frontal-offset, side-impact and roof-strength crash tests.

The sheer brute force of the 2013 BMW M5's V8 is enough to leave you shaken and breathless; even so, the power plant delivers this thunder with grace and sophistication. As a result, this sedan is always a pleasant and easy companion, whether driven hard on winding blacktop or at a leisurely clip during mundane city travel. While the V8's engine note isn't quite as commanding as one would hope, its throaty rumble offers lots to enjoy.

This M5's DCT is a worthy match for its impressive engine. You can choose to shift gears by tapping the rubber-backed shift paddles on the steering wheel or by nudging the console-mounted lever back and forth. Either way, the process is executed so quickly, smoothly and intuitively that the quick but unrefined single-clutch SMG system seems clumsy and low-tech.  But as is the case with a lot of modern BMWs, no shift schedule within the system seems to be ideal. In particular, the normal mode seems too sleepy for the car's character, as if mpg were far more important than mph.

For the M5, BMW has retained its traditional hydraulically assisted power steering, even though electric power assist is part of the current 5 Series. The car feels far livelier than a conventional 5 Series as a result.Of course this is a great big sedan, not a sports car, so it's best experienced where the road is open enough to let the car open up a little.

Materials quality is acceptably tony within the M5, with expanses of buttery leather and gleaming aluminum. The cabin design seems a bit stark when compared to that of rivals like the Audi S6 and JaguarXFR, however. The iDrive electronics interface works well for wrangling all of the M5's systems, but it can come off as rather complicated; some rival systems are easier to use.

This BMW's meaty sport seats feature 16-way adjustment, allowing for highly customizable support. A roomy backseat offers practicality that's a pleasant surprise in a car this sporting, and is spacious enough to ensconce adults over long drives without discomfort. A split-folding rear seat enhances the trunk's 14-cubic-feet cargo capacity.