Introduction

Inside and out, the shapely Mercedes-Benz CLS midsize four-door not only looks great, it exudes a virtually timeless appeal. With the CLS, the German automaker helped popularize what's been called the modern four-door coupe design phenomenon. That is, a four-door sedan with a sloping roofline resembling that of a stylish two-door coupe. 

Little has changed since a significant revamp for the 2012 model year. During 2016, Mercedes-Benz has been gradually making its excellent 9-speed automatic transmission standard equipment, starting with the V8-powered CLS550. 

Mercedes-Benz also offers a CLS400 with a V6 engine, plus a super-powered AMG CLS63 S that promises startling performance and handling qualities. A new Night Package for the AMG model blacks out some chrome trim. 

All powertrains are potent and capable. The Mercedes-Benz CLS400 gets a 3.0-liter twin-turbocharged V6 engine rated at 329 horsepower and 354 pound-feet of torque. A brisk performer, the CLS400 never lags in traffic, and passes easily at any speed. 

The Mercedes-Benz CLS550 uses the familiar 4.6-liter twin-turbocharged V8, here developing 402 horsepower and 443 pound-feet, yielding even more vigorous acceleration. 

Both CLS versions come with either rear-wheel drive or 4MATIC all-wheel drive. 

The Mercedes-Benz AMG CLS63 S 4MATIC features a twin-turbo 5.5-liter V8 that cranks out 577 horsepower and all-wheel drive to tame the beast. 

Initially installed only in rear-drive CLS550 models, the 9-speed automatic transmission goes into 2016 CLS 4MATIC versions as well. For now, at least, the CLS400 retains a 7-speed automatic. So does the AMG model. 

Mercedes-Benz's latest interior design theme looks great in the CLS, enveloped in luxurious leathers and woods, seamlessly melding classic and high-tech themes. The large, luxurious cabin blends with its exquisite body, potent powertrains, and high-tech features. On the other hand, back-seat headroom is somewhat tight, at least for taller riders. 

Standard equipment includes the Mercedes-Benz Audio 20 CD system, with Bluetooth audio streaming, satellite radio, a Gracenote music database, plus 10 GB of hard-drive music storage. Upgrades include a 610-watt, 14-speaker harman/kardon LOGIC7 surround-sound system, and a costly Bang & Olufsen setup. 

The CLS has not been crash-tested by either federal safety officials or the independent Insurance Institute for Highway Safety. 

Mercedes-Benz invariably provides abundant technology, much of it safety-related. Plenty of entertainment, information, and safety features are included or available. Mercedes-Benz's COMAND system, with an 8-inch color display, is not universally acclaimed. 

Lineup

The 2016 Mercedes-Benz CLS400 ($66,900) and CLS400 4MATIC ($69,400) include the V6 engine, 7-speed automatic, leather upholstery, heated front seats with driver's memory, a sunroof, auto-dimming mirrors, bi-xenon headlights, wood interior trim, adaptive air suspension, and 18-inch wheels. Option groups can add a rearview camera, blind-spot monitoring, and lane-keep assist. 

The Mercedes-Benz CLS550 ($74,100) and CLS550 4MATIC ($76,600) uses the 402-horsepower V8 engine and 9-speed automatic, and upgrades including harman/kardon audio and navigation. 

The Mercedes-Benz AMG CLS63 S 4MATIC ($107,800) features a 5.5-liter, 577-horsepower V8, as well as Collision Prevention Assist, an Alcantara headliner, and AMG-specific wheels. 

Ten airbags are standard on each model. So are Attention Assist and Collision Prevention Assist Plus, with autonomous braking. Safety options include adaptive cruise control, Pre-Safe Brake with pedestrian detection, blind-spot monitors, lane-keep assist, Night View Assist, and parking assistance. 

Walkaround

One of the first models to adopt the coupe-sedan concept, the Mercedes-Benz CLS remains among the best examples. Despite being last updated for 2012, the coupe-like look of this four-door is far from outmoded. Tradition-minded critics have uttered some harsh words about calling four-door cars coupes, but other automakers, including Audi and BMW, have embraced the idea. 

Basically, a long, arching curve defines the car's silhouette. Short overhangs, front and rear, intensify the sleek coupe-like profile. Only up front is the CLS starting to look a trifle past its prime, though the clean, sharp front-end lines reveal a kinship to its E-Class cousin and the entire Mercedes-Benz family. 

Pay a hefty premium for a carbon-fiber package, and the CLS looks even more menacing. AMG models reach further into audacious form, brandishing larger air intakes and more aerodynamic elements. 

Interior

Adapting themes from the latest C-Class and S-Class, the CLS interior is defiantly upscale. Trim elements in genuine wood and rich metal add to the luxurious nature of the cabin. 

Up front, the interior presents a welcoming appearance. Roomy and comfortable bucket seats offer ample adjustment for taller occupants. In upper trim levels, active bolstering hugs passengers during cornering, providing even greater support. 

Back seats are snugger, causing taller passengers to feel cramped. Inevitably, a swooping roofline comes at a price. Headroom is sacrificed, even if average-size adults fit in back fairly readily. 

Leather upholstery is standard. Plastic elements are high-quality, while display screens qualify as stunning. For 2016, Mercedes has made Nappa leather available. Thus, AMG riders can experience even richer textures, as well as special touches that furnish an unmistakable sense of ultimate performance. 

Interior storage isn't as accommodating as might be expected. A number of small items can fit into the center console, and the trunk holds only 11 cubic feet. 

Driving Impression

The entire CLS model is compelling. Each offers the sort of performance found in various familiar rivals, including the Audi A7. 

Despite its position at the bottom of the performance range, the CLS400 is no slacker. Rather, it delivers briskly swift, lively acceleration at any road speed. 

Quicker yet is the CLS550, whose 9-speed automatic provides smooth shifts as well as sensible gear selections along the way. 

For a large coupe-sedan, the AMG CLS63 S supplies near-supercar acceleration plus impressively precise handling, courtesy of the adaptive suspension. In S trim, the AMG twin-turbocharged V8 whips up 577 horsepower and 590 pound-feet of torque. 

Each CLS model promises comfortable, relaxed cruising, along with the ability to ease gracefully through curvy roads, impressive for a car of its size. If absolute limits should be called for, AMG models are ready to comply. 

Visibility is mostly good. Depending on driver height, though, rear three-quarter views may be compromised by the low roof and thick back pillars. Here, the standard rearview camera and parking-assist systems can help. 

Thrifty operation isn't a strong point, but the rear-drive CLS400 is EPA-rated at a relatively frugal 20/30 mpg City/Highway, or 24 mpg Combined. All-wheel drive sinks those estimates substantially, to 19/26 mpg City/Highway, or 22 mpg Combined. The rear-drive CLS550 is EPA-rated at 17/26 mpg City/Highway, or 21 mpg Combined, dropping to 17/25 mpg City/Highway with all-wheel drive. 

Quick and loud as it is, the AMG manages 16/22 mpg City/Highway, or 18 mpg Combined, and that's with all-wheel drive. 

Summary

The CLS is well-equipped, but prices are hefty and a number of costly upgrades can be added. In its most expensive automobiles, Mercedes-Benz typically makes plenty of comfort, convenience, and technology features standard. 

Driving impressions by Aaron Cole, The Car Connection. James M. Flammang contributed to this report.