CLS 63 AMG

With any new Mercedes-Benz comes, sooner or later, the inevitable AMG version, some of which seem appropriate and some gratuitous. We count the new, second-generation CLS four-door coupe among the former. Like the CLS on which it's based, the 2012 CLS63 AMG re-interprets its predecessor's restrained lines with a more expansive, aggressive approach. The snout draws from the gull-winged SLS, and a steep windshield flows into an arching roofline, meeting a muscular rear haunch that culminates in a tail with deep overhangs. The look is husky and mean, offering more gravitas than its delicate looking progenitor.

The hand-built AMG powerplant has been downsized to 5461 cc, but the V-8 gains twin turbos, yielding bumps in horsepower and torque-518 hp and 516 lb-ft, or 550 hp and 590 lb-ft with the optional performance package. Turn a blind eye to the curiously stubborn 6.3 designation-which was never quite right anyway, since its naturally aspirated predecessor displaced 6208 cc-and it's hard to find fault in the new powerplant, which manages a 32 percent gain in fuel economy. EPA figures of 16 mpg city and 21 mpg highway help the smaller motor dodge a $3000 gas guzzler tax, aided in part by a stop/start system that shuts off the engine when stationary.

The CLS63 still feels intimate and-well, coupelike inside, though there's more space than you might expect for such a rakish silhouette. Nestled in the rear seat, a five-foot, eleven-inch person fits comfortably below the roofline, with sufficient legroom to allow a relaxed posture. Piano black details meet touchstones like burled walnut trim and an IWC timepiece that's a nod to Art Deco glamour. The performance package gains edgier exterior details, carbon fiber interior panels, and a steering wheel partially wrapped in Alcantara, as well as the power-enhanced engine and carbon ceramic brakes.

Though acceleration is appropriately willing under light throttle, a stab of the gas punches this 4114-lb car through space with tenacity, good for 0-to-60-mph jaunts in a claimed 4.4 seconds, or 4.3 ticks with the performance package. In contrast to the standard issue CLS, the CLS63's seven-speed transmission ditches a torque converter for a wet startup clutch, and shifts occur smoothly and swiftly, with extra alacrity and added steering stiffness when you click from "C" (comfort) to "S" (sport), S+, or M (manual.) Ride quality is firm and sometimes jarring, getting stiffer with more aggressive settings. But high entry speeds are rewarded with surprising feedback from the electromechanical steering, making this sixteen-foot car feel taut and nimble on tight roads. The "AMG" button amps up everything from shift times to suspension damping, offering downshifts that are seemingly prescient and shotgun-quick. Though not quite as aurally expressive as the normally aspirated 6.2-liter engine, the new twin-turbo nonetheless grunts and growls and snorts between shifts.

The engine's stop/start feature only activates in "C" mode, and sudden throttle can produce abrupt lurches from a standstill; it's best to ditch Eco mode if you prefer quick, smooth getaways. While our performance package-equipped tester may have felt incrementally quicker (or was our interior dynamometer simply drunk on horsepower?), its massive carbon ceramic brakes definitely added a more dramatic bite to deceleration, as though all four tires were digging in like cleats on Astroturf.

Bulked up but not brawned out, the 2012 CLS63 offers an appreciable improvement in speed, fuel economy, and, arguably, styling over its antecedent. The first-generation CLS apparently needed time for consumers to become accustomed to its then-radical shape, as it had its best sales in 2010, its last full year on the market. Based on our drives of both the regular CLS and the new CLS63, both of which hit dealers in June, it seems that Mercedes-Benz has another hit on its hands-long adoption curve, or not.

2012 Mercedes-Benz CLS63 AMG 
On sale: June 
Price: (estimated) $100,000 
Engine: Twin-turbocharged 5.5-liter V-8, 518/550 hp, 516/590 lb-ft 

Drive: rear-wheel