The following review is for a 2012 Model Year. There may be minor changes to current model you are looking at.

Still the big dog.Fresh looks, new engine, comfortable for daily driving.

Introduction

The 2012 Mercedes Benz S-Class remains the prototypical full-size luxury sedan, and the complete luxury package. It's suitable for quiet, rock-steady cruising at Autobahn mega-speeds, spirited drives through the countryside, unflustered dawdling through heavy traffic or chauffeured escape from the grind. S-Class safety systems are unparalleled, and this sedan is huge inside. 

The 2012 S-Class introduces some substantial changes. Among them: three new engines and a redesigned 7-speed automatic, all intended to improve fuel economy while preserving the requisite power and verve. However, the biggest news for 2012 is introduction of the first diesel-powered S-Class for North America since 1996. 

The S-Class competes with the Audi A8L, BMW 7 Series and, to a lesser extent, the Lexus LS, but the S-Class offers more model choices than any of those other models. The sport-tuned S63 AMG matches up with BMW Alpina B7, and the smaller but sportier-handling Maserati Quattroporte, Porsche Panamera and Aston-Martin Rapide. The S65 makes a less-ostentatious (and faster accelerating) alternative to Bentley's Flying Spur Speed. Mercedes offers the most engine choices in this class, and optional 4MATIC all-wheel drive. 

The 2012 Mercedes-Benz S350 BlueTEC is powered by a high-tech, low-emissions 3.0-liter turbo-diesel V6. It's arguably the smoothest, quietest diesel engine ever, almost imperceptible from the driver's seat, and its 455 pound-feet of torque allow the Mercedes-Benz S350 to scoot from 0-60 mph in 7 seconds. Based on the EPA's projected ratings of 20/31 mpg City/Highway, the S350 BlueTEC beats the next highest mileage car in this class by 20 percent (including a couple of hybrids), and that's with 4MATIC all-wheel drive as standard equipment. 

The 2012 Mercedes-Benz S400 Hybrid combines a gasoline V6 with an electric motor for nearly 300 horsepower, powering the car to an electronically limited top speed of 130 mph, and surpassing all but the new BlueTEC diesel in fuel economy. This mild hybrid won't run strictly on electric power. The motor assists the gasoline engine to conserve fuel and converts braking energy into electricity to power accessories The S400 Hybrid is EPA-rated 19/25 mpg. 

The 2012 Mercedes-Benz S550 gets a new, smaller twin-turbo V8, with more power (0-60 mph in 5.4 seconds), better mileage and optional all-wheel drive. The S600 is the most luxurious S-Class, powered by a 536-hp, 5.5-liter twin-turbo V12 fitted with a 5-speed automatic. 

The S63 AMG is finished by the in-house tuning department with appearance tweaks, 20-inch wheels and firmer sport suspension. The 2012 S63 AMG is powered by a 5.5-liter twin-turbo V8 generating 536 horsepower and 500 lb-ft of torque. It also features a unique clutch-operated 7-speed automatic. The S65 AMG is AMG's treatment on the V12 S-Class, with a 6.0-liter engine delivering 621 horsepower and 738 lb-ft of torque. It's one of the most powerful four-door cars in the world. 

The S600 V12 and the S63 AMG are both a second quicker than the S500, while the S65 AMG is quickest of all (0-60 in 4.2 seconds). Approaching its 186-mph speed limiter, the S65 is still pulling like a freight train. 

We've found all the S-Class models handle well for big luxury sedans. They are composed, responsive and stable at any speed. The Airmatic air suspension system has both automatic and manual controls for ride height and firmness. The transmissions offer multiple operating modes, for best comfort and economy or maximum driver involvement and performance, while brakes bred for the Autobahn have massive reserves at more pedestrian American speeds. 

Technophiles may revel in the best night vision system on the market, cruise control that will maintain following distance up to 125 mph or stop the car automatically, and seats that massage, cool and self-inflate under lateral loads. Even the least expensive model comes with everything most buyers want, including a navigation system and a high-grade, high-watt harman/kardon surround system with all the right hardware. 

Inside, occupants are surrounded by wood, leather and finishes befitting an expensive car, not to mention serene quiet at cruising speeds. The trunk is one of the largest in this class, and perfectly shaped for maximum storage, and the rear seat is truly expansive. It's also loaded with standard niceties, including lit vanity mirrors, ambient lighting and multiple air vents. The rear cabin can also be upgraded with adjustable, ventilated seats and a killer two-screen video system. 

The S-Class rolls near the tip of the luxury pyramid, at a premium but largely justifiable price. Whether you prioritize hybrid cleanliness or incinerating power, its general air of superiority makes a compelling argument to anyone shopping a true luxury sedan. The Mercedes-Benz SLK350 is the smaller and less-expensive of the marque's two-door roadsters. The SLK350 features a retractable hardtop that shuts out the weather when up and allows for the freedom of open-air driving in just 20 seconds. In price and performance the SLK350 competes with the Audi TT, BMW Z4, and Porsche Boxster. 

The 2012 Mercedes-Benz SLK-Class features fresh looks inside and out and a new engine, though the platform isn't substantially new. 

Initially, a new 3.5-liter V6 is the only engine available. It replaces another 3.5-liter V6, but adds direct engine and changes from a 90- to a 60-degree configuration, which is the ideal design geometry for a V6. Horsepower and torque are up slightly, but fuel economy is improved by 12 percent. The lone transmission is a 7-speed automatic that can be shifted manually with steering wheel paddles. 

Due in early 2012 is the SLK250, which will feature a 201-horsepower turbocharged 1.8-liter four-cylinder. Following soon thereafter will be the SLK55 AMG, which will get a new 415-horsepower 5.5-liter V8. 

In basic V6 form, the SLK350 is quite quick, but not as fast as higher end models from its competitors. The new engine has a pronounced exhaust note that is probably the rawest aspect of the car. 

Handling is impressive, though not quite as sharp as that of the Porsche and BMW competition. The steering isn't razor sharp just off center but it gets quicker as the steering wheel is turned thanks to Mercedes-Benz's Direct Steer. It's a great system that aids handling in sharp turns. While the Boxster and Z4 may be sportier, the SLK-Class is the most comfortable car in its class, with a quiet, stable ride. 

Inside, the SLK-Class offers the typical high-quality Mercedes-Benz cabin featuring an attractive design and top-notch materials. Room is good for all but tall drivers, who will want more seat travel. The folding hardtop limits trunk space, but there is still enough room for a weekend away. 

The 2012 Mercedes-Benz SLK350 delivers agile handling, ready power and a smooth ride. Driving enthusiasts, however, will be better served by the Porsche or the performance version of the BMW. 

Lineup

The 2012 Mercedes-Benz S-Class includes seven models distinguished by their engines and drive systems. All come standard with an automatic transmission, and two offer 4MATIC all-wheel drive. The most powerful models are saddled with a federal Gas Guzzler Tax. 

S-Class standard equipment includes leather upholstery and real walnut trim, dual-zone automatic climate control, 14-way power front seats with heating, ventilation and memory, voice-operated navigation with on-board hard drive, sunroof and a full complement of power accessories. The standard audio is a 600-watt, 15-speaker harman/kardon Logic 7 surround system with CD changer, HD and satellite radio, an SD card slot and Bluetooth. All models feature an air-spring suspension with ride height adjustment, and most come standard with 18-inch alloys wheels. The S350 BlueTEC 4MATIC ($93,425) is powered by a 240-horsepower, 3.0-liter turbo-diesel V6. The transmission is a 7-speed automatic. 

The S400 Hybrid ($92,725) uses a gasoline-fueled 3.5-liter V6 and an electric motor, combining for 295 peak horsepower. 

The S550 ($95,375) gets a direct-injection twin-turbo 4.6-liter V8; The S550 4MATIC ($98,375) adds all-wheel drive. 

Options for these S-Class models are vast, though many are clustered in packages. Popular groups include the Premium package, which adds Parktronic guidance, Keyless-Go proximity key, massaging seats and a back-up camera. The Sport package adds racy AMG body work and 19-inch wheels. The Rear Seat package includes four-zone temperature control and 8-way power heated and ventilated rear seats, while the Rear Entertainment package adds two rear-seat video screens with DVD, remotes and multiple methods for connecting external devices. Stand-alone options are even more plentiful, ranging from 20-inch wheels to a wood/leather steering wheel to a Splitview front video monitor. Custom S-Class options include non-standard paint colors and upholstery material. 

The S600 ($160,375) is powered by a 536-hp, 5.5-liter twin-turbo V12 with a 5-speed automatic. The most luxurious S-Class, the only standard options are larger wheels, the Splitview video screen and special paint. 

The S63 AMG ($140,175) features 20-inch wheels and sports suspension along with a 5.5-liter twin-turbo V8 generating 536 horsepower and 500 lb-ft of torque plus a special clutch-operated 7-speed automatic. The S65 AMG ($211,775) features the AMG-tuned V12 S-Class delivering 621 horsepower and 738 lb-ft of torque. 

Safety features include eight airbags: front-impact airbags, side-impact airbags for both front and rear passengers, and head-protection curtains on both sides of the cabin. The Pre Safe system senses an impending collision and loads the brakes, tightens the seatbelts, closes the windows and sunroof and repositions the front passenger seat for optimal crash protection. The mbrace telematics can automatically report an accident and summon help. Active safety features include advanced skid control (electronic stability control) and anti-lock brakes (ABS). 

Safety related options include Attention Assist, which identifies the erratic steering corrections drivers make as they begin to get drowsy and triggers an audible warning. Active Lane Keeping Assist warns when the S-Class drifts from its lane, while Active Blind Spot Assist identifies vehicles not visible over the driver's shoulders. Both incorporate an intervention feature, helping correct the car's course if the driver doesn't heed the initial warning. Distronic Plus cruise control can automatically stop the car from up to 125 mph. Night View uses an infra-red camera, creating a black-and-white image of the road and people ahead in darkness, and projecting that image in the center of the dash. 4MATIC all-wheel drive improves stability in slippery conditions. The 2012 Mercedes-Benz SLK-Class is initially offered in only one model: the SLK350 ($55,675), powered by a new 3.5-liter V6 engine that makes 302 horsepower and 273 pound-feet of torque. The lone transmission is a 7-speed automatic that can be shifted manually with steering wheel shift paddles. 

Standard equipment includes leather upholstery, air conditioning, interior air filter, cruise control, 8-way power seats with lumbar adjustment, power tilt/telescoping leather-wrapped steering wheel with audio controls, heated power mirrors with turn signals and driver's side auto-dimming, power windows, power locks, remote keyless entry, AM/FM radio with 6-disc CD/MP3 changer, HD radio, auxiliary input jack, Bluetooth audio streaming and wireless cell-phone link, mbrace assistance system, trip computer, rain-sensing wipers, universal garage door opener, automatic headlights, theft-deterrent system, cloth windscreen, sport-tuned suspension, rear fog lights, and P225/40R18 front and P245/35R18 rear tires on alloy wheels. 

Options start with Premium Package 1 ($2,590), which includes heated front seats, AirScarf neck-level heating, a Harman Kardon sound system, an iPod interface, satellite radio, and remote control for the retractable roof. A Multimedia Package ($2,150) adds a navigation system with voice recognition and real-time traffic information, the Mercedes COMAND control screen, an SD card reader, and a 10-gigabyte music hard drive. A Dynamic Handling Package ($990) adds a Sport button to control an adjustable suspension. A Sport Package ($2,500) comes with red interior ambient lighting, AMG wheels, and more aggressive AMG-designed front air dam, side sills and rear apron. The Distronic Plus Package ($2,685) includes Pre-Safe crash safety system and adaptive cruise control. A Lighting Package ($1,090) adds adaptive bi-xenon headlights with washers, and a Wood Trim Package ($990) brings Burl Walnut wood interior trim and a wood and leather-wrapped steering wheel. Stand-alone options consist of front- and rear-obstacle detection ($970), dual-zone automatic climate control ($760), Keyless Go keyless access and starting ($650), a glass panel roof ($500), Mercedes' new Magic Sky Control roof ($2,500), a Plexiglas windblocker ($350), illuminated door sills ($700), and the AMG alloy wheels ($500). 

Safety features include dual front airbags, side airbags, knee airbags, active head restraints, roll bars, tire-pressure monitor, Attention Assist, anti-lock brakes with brake assist, traction control and electronic stability control. 

Walkaround

Traditionally, Mercedes-Benz styling evolves slowly, with minimal changes year to year and only moderate changes with complete redesigns. That still holds with the flagship S-Class sedan. Its shape and body panels haven't changed since the current version debuted in 2007, but it still looks elegant and contemporary. 

The S-Class is a big car. It's longer, with a longer wheelbase, than a honking Hummer H2 SUV, for example. It also fills a bit more floor space than either of its primary competitors, the Audi A8L and the BMW 7 Series, and Mercedes uses a variety of materials to keep the S-Class's weight under control. Its hood, door skins, and front fenders are aluminum, as are the engine, transmission and most major suspension components. The trunk lid is made of a plastic composite, and its structural innards are largely high-strength steel. An S-Class isn't a bad place to be in a crash. 

The basic S-Class shape has discernible fender flares front and rear, a classic grille laid informally back and a general flow similar to its ultra-lux Maybach sister-brand. Its lines pay off in minimal wind noise and aerodynamic drag, high-speed stability, and an air of exclusivity enhanced by key details, starting with chrome strips framing the glass and rear doors more than four feet long. 

Other details are anything but ordinary. Gaps and transitions in the body are subtle, minimizing the disruption of airflow over the surface. There isn't a sharp edge anywhere. The side mirrors fold narrower than the widest part of the car. Positive stops keep the doors open at any position you move them to, and they essentially suck themselves shut, so you needn't slam them. The keyless entry works effectively for all doors and the trunk. 

Exterior changes to the current S-Class have largely been reserved to the array of exterior lights, and more for practical benefit than style. LED elements have grown more prominent, with bright-white daytime running lights in the lower bumper, standing lights, and parking lights that switch to amber for front turn signals. The taillights, once divided by body color strips, are now full LEDs. V12 models feature adaptive brake lights that blink rapidly during heavy braking. 

The S-Class line offers multiple wheel styles, from 18 to 20 inches in diameter, and the larger wheels are available on all models. The big wheels look fabulous, and they can improve handling, or specifically steering response. But the payback is significant. The large rims mean shorter tire sidewalls, so they don't as readily shrug off potholes. The low-profile tires are nosier. They generally detract from ride quality, cost more to replace, and limit the use of tire chains or even winter tires in snowy climes. 

There are some subtle model distinctions. The S400 hybrid has a HYBRID logo on the trunk lid and BlueEfficency badging on the front fenders. The S600 gets V12 badges on the fenders and dual double-square tailpipes. The racy AMG models have more aggressive air management devices, with more visual mass to the lower bodywork and a deeper grille. They're finished with quad-oval tailpipes. The V12 BITURBO badge on the S65's fenders should make mere mortals think twice before offering to run for pink slips. The 2012 Mercedes-Benz SLK-Class features the classic sports car silhouette, with low stance, long hood, and short rear deck. The design, which appeared on the high-performance 2011 SLS AMG, takes cues from the 1955 190SL, with a pronounced, upright grille. The large grille features the Mercedes star, which can be interpreted as the front view of a propeller, and it is flanked by bars that look like airplane wings. Daytime running lights are standard, and self-cleaning, adaptive bi-xenon headlights that point into turns are optional. 

The car is 1.5-inches wider this year, 1.5 inches longer and it sits a half inch lower. The front fenders sport side gills which are new to the SLK-Class, but are recognizable from the larger SL-Class. The rear end features an integrated trunk spoiler and LED taillights. The overall look is more masculine, which is just what the SLK-Class needed. 

The retractable hardtop is easy to operate, but it doesn't work while the car is moving as similar tops do on some competitors. It goes up or down in a tidy 20 seconds. The top is offered with a body-color roof panel, an 80-percent tinted clear panel or the new Magic Sky Control roof. This industry first option features a tinted film with particles that can be charged. Press a button to send a charge through the film and it reduces the tint to 80 percent, letting in lots of light. When uncharged, the particles flatten out, increasing the tint to 95 percent, darkening the view above considerably, and helping to keep the car cool on a hot day. Magic Sky Control is a cool little innovation, but at $2500 it's more of a curiosity than a wise option choice. 

Interior

The Mercedes S-Class cabin is like a cocoon, or perhaps more appropriately a vault, that wraps its occupants in quiet, comfort and every amenity one can reasonably expect. Yet if there's a single predominant impression inside the S-Class, it's space. Unlike its competitors, the S-Class for North America is offered only in its long-wheelbase version, with capacious room up front and even more behind. 

The interior finish is appropriate to this class of automobile, and the choice of materials is expansive. All S-Class cars have leather seating, though there are several grades available, and more money usually brings an Alcantara headliner as well. There has to be plastic somewhere, but it's difficult to spot. The giveaway point on most cars, the pillar between the doors, is carpeted about a third of the way up in the S-Class and then covered in headliner material. Trim choices range from contemporary piano-black lacquer and ribbed brushed metal to more traditional wood-grain and chrome. Some of the high-gloss surfaces glare in the sun, but there are very few flat surfaces, and details stand out throughout. Note the chrome lip on the strip of wood sweeping across the dash and doors, or how the woodwork bends around the controls and console, or how the center console opens from either side. Visibility is very good for the driver, thanks to expansive glass, a sloping hood and well- placed roof pillars. Standard bi-Xenon adaptive headlights and eight heated windshield washer jets certainly help, as do the optional parking sensors and rearview camera. If the back seat is empty, the rear headrests drop out of sight at the touch of a driver's button. 

The standard 14-way powered front seats are heated and ventilated, with three memory settings each side. The wide range of adjustment includes seat-cushion length. Switches shaped like miniature seats are mounted on the doors to ensure easy reach and operation. Some adjustments, like recline, will also adjust headrest height automatically, but as it is with many S-Class controls, you can manually override if you wish. 

The optional Drive Dynamic front seats add further adjustments for cushion, backsides, lumbar and shoulders, plus four varieties of massage,. These amount to a sport seat with the comfort of a fine armchair, and they can automatically inflate side bolsters relevant to cornering load to hold you in place. We found this feature distracting when cornering, so we turned it off, and still kept the massage going. 

The gauge package provides standard data, with speed, tachometer, fuel level and coolant temperature. The central speedometer is a video image, rather than a rotating mechanical needle. The center portion can display everything from navigation or audio info to driver assists and mpg to lap times in the AMG cars, called up via thumb buttons on the steering wheel spokes. With Night View engaged, the screen shows an image of the dark road ahead with pedestrians highlighted, adding speed along the bottom and warning lights superimposed around the periphery. Its central line-of-sight location and crisp image make Night View better than other night-vision enhancements that rely on thermal imagery. 

Primary driving controls are on the steering column, with a PRND shift stalk on the right, and up/downshift paddles on either side (close to the wheel, with little finger space between). On the left are stalks for cruise control, wheel tilt/telescope, and a busy one with turn signals, high beams, wipers and washers. We don't understand Mercedes' longstanding commitment to its odd cruise-control stalk, because it doesn't work very well. The eight-position, dash-mounted light switch has off and automatic modes, but even in off the headlights were often on in daylight, and that was after we consulted the six-page owner's manual entry on the lights. 

Most of the other buttons are located in a bulging pod below the standard navigation screen. The screen sits top and center, and can be adjusted for brightness separately from the other instruments. It's well shaded, and can be angled toward driver or passenger. The optional Splitview screen is a potentially marriage-saving device that allows the driver to see one full-size image (map, radio, seat control) while the front passenger sees another (a movie with headphones or map if they're navigating) simultaneously on the single central screen. Don't ask us how they do it. 

Climate controls are arrayed below the screen. The S-Class provides true dual-zone operation, not merely independent temperatures. The system allows a choice of how airflow is layered and distributed through the cabin, lest the driver prefer foot-well flow and the passenger dash vents. There are hard buttons for temperature adjustment and fan speeds, but if you want to direct airflow in any fashion except defrost or automatic, you'll have to delve into the point-and-click control system. 

Mercedes-Benz calls its central control system COMAND. It uses a round knob that rotates and moves in three dimensions, a mouse-shaped palm rest that hides a 10-key, phone-style pad, and four quick-access buttons across the front. There's a thumbwheel to control audio volume as well, and while it's easy to find, it's hidden from the driver's view by the palm rest. 

COMAND uses series of menus and scrolls to adjust hundreds of things, and every operation appears on the video screen. You can rotate the COMAND knob to change radio stations, or use the keypad to punch in the number directly. Overall, the system is a decent balance of old-fashioned mechanical buttons and point-and-click menus, and probably less complicated than some others. We'd rank it a notch below Audi's MMI interface and a couple of notches above BMW's iDrive. 

The S-Class comes standard with a 600-watt, 15-speaker harman/kardon Logic 7 surround-sound system, including a 6-DVD changer, memory card and satellite radio receiver. Auxiliary inputs are out of sight in the glovebox and run through the COMAND screen. An analog clock rides center dash, branded by watchmaker IWC Schaffhausen Ingenieur in AMG models. Cabin storage includes a sizable pocket in each door, smaller pockets within the front door armrests, center console cupholders and bins, and the glovebox. 

The three-place rear seat is huge. With a 6-foot, 3-inch driver, we measured more than a foot of space from front seatback to rear seat cushion. It's also well-stocked with amenities, including four adjustable AC vents, separate cabin and reading lamps, overhead lit vanity mirrors, and the same adjustable ambient lighting as the front, hidden below the woodwork strips. There's a storage area behind the center armrest, and a standard power-operated rear-window shade. Power shades for the rear side windows are optional. 

If your clients or kids are worth it, the rear-seat upgrade package adds left/right rear climate control and heated and ventilated power-adjustable outboard seats. This setup provides the utmost in comfort while maintaining five-passenger capability. On S-Class cars so equipped, the driver can control adjustment of the seat behind. The right rear passenger (the boss position) can control the right front seat for additional legroom. The entertainment package adds a height adjustable screen behind each front headrest, with video inputs and a DVD drive under the center rear seat. It comes with dual wireless headphones and an individual remote for each screen and the car's main audio system. 

Mercedes has changed the published capacity of the S-Class trunk from 19.8 to 16.4 cubic feet. Where the extra space went, we're not sure, because the trunk remains as roomy as ever, and still roomier than that in the Audi A8 (13.2 cubic feet) or BMW 7 Series (14 cubic feet). The trunk space is ideally square-angled and tall, and therefore holds more cases and bags than many vehicles with greater listed capacity. The S400 has the same trunk space as the non-hybrid S-Classes, because its relatively compact battery is under the hood. Like other Mercedes models, the SLK-Class interior is replete with top-notch materials. There are no hard plastic surfaces or wide panel gaps. The dashboard, armrests and center console are all soft to the touch, and the design is made more interesting by contrasting colors. Real aluminum or burl walnut wood trim add to the look, as does the red ambient lighting included with the Sport Package. The gauges, which feature gray numerals on a white background with aluminum trim rings, have a classy watch-like quality. These gauges straddle a digital display that shows trip computer, outside temperature and other vehicle information. 

Like other luxury cars, the SLK-Class features a central control interface. Mercedes calls it COMAND, and it uses a rotating knob on the center console to control the communications, navigation and entertainment functions. A series of buttons on the center stack makes getting to each area easier, but it will still take awhile for the uninitiated to get used to the system. It may be a bit complex, but it eliminates the need for many hard-to-find buttons. After several turns in various Mercedes, we've gotten used to COMAND, but it took longer to learn than BMW's iDrive system did. 

Appropriate for a sports car, the seats are comfortable, supportive and have thick enough bolstering to keep occupants in place in fast corners. Head and legroom are plentiful for average size occupants, but tall folks might want more seat travel. You won't want to put the seat back all the way because it rubs up against the rear bulkhead and causes an annoying squeaking sound. Cool weather comfort is aided by the available AirScarf system, which blows warm air on passengers' necks. It's a bit of a help on a cool day, but it won't make you want to drive with the top down when it's under 50 or 55 degrees outside. 

The retractable hardtop does a good job of shutting out noise when up, and visibility is good with the top up, too. The SLK offers two types of windblockers. The standard cloth windblocker works just fine and an optional version with two fold-down Plexiglas wings works just as well while offering better rear visibility. Neither version, however, will shut out enough wind to make cell phone calls possible at highway speeds when the top is down. 

While the top takes up some trunk space, the SLK has a decent 6.4 cubic feet of cargo volume. As we found out, that is just enough to hold two pieces of carry-on luggage and two laptop bags. 

Driving Impression

The Mercedes S-Class does everything a true, full-size luxury sedan should, and we might describe it as a complete automobile. If you need something, the S-Class almost certainly has it. If you want it to do something, just about anything, the S-Class can probably get it done. 

Every S-Class delivers better than adequate power and performance in smooth, quiet, rock-steady fashion. Virtually all of its luxury or high-tech features are offered on all models, so how much better than adequate the performance gets depends on the buyer's budget or penchant for satisfyingly wretched excess. 

There are substantial mechanical changes to the S-Class line-up for 2012, starting with three new engines intended to improve fuel economy without sacrificing power or performance. The standard seven-speed automatic has also been re-designed, basically for the same purpose. This transmission is engineered to help ensure that more of the engine's power gets delivered to the wheels to move the car, rather than bled off in the transition (and wasted) as friction and heat. 

The highlight for 2012 is introduction of the S350 BlueTEC, the first diesel-powered S-Class available in North America in 16 years. It's driven by an advanced, 240-horspower, 3.0-liter turbo-diesel V6 engine through the seven-speed automatic, with standard 4MATIC all-wheel drive. 

Mercedes' V6 turbodiesel is the smoothest, quietest diesel engine available, so virtually all the smoky, clattering drawbacks of more traditional diesel power are gone (though the oily diesel smell during fill-ups remains). The S350's 240 horsepower is impressive by diesel standards, and if it seems a bit light (or the engine a bit small) for a car the size of a Hummer H2, don't sweat it. This engine produces 455 pound-feet of torque, and it's the twisting power of torque that generates acceleration. Dip the accelerator pedal on the S350 BlueTEC and it jumps, with enough force to snap the head back into the headrest. 

The S350's overall performance is virtually identical to the gasoline-powered S400 Hybrid, with even stronger short bursts of acceleration, and the diesel engine comes with a substantial fuel mileage increase compared to the hybrid, or any other car in this class (projected at 20 mpg city, 31 highway, according to the EPA). And that's with standard all-wheel drive, which works against fuel economy. Not that long ago, a 31 mpg highway rating was the domain of much smaller, slower cars. If our usual travel circle left access to diesel fuel, we wouldn't have a second thought about choosing the S350. 

The S400 Hybrid does not meet some definitions of hybrid because it won't propel itself on electric power alone. Essentially, it uses its electric motor to add power without using more fuel, and it does improve mileage compared to the V8 models (19 mpg city, 25 highway, though we recorded 21.7 around town and 27.6 on the highway). Its compact lithium-ion battery is in the engine compartment, and the S400 weighs only 19 pounds more than S550. With a combined power output of 295 hp and broad torque delivery, its acceleration betters most hybrids, and it hits 60 mph from a stop in just over seven seconds. A hybrid- status dash display let's the S400 driver know what the electric motor is doing and how the battery is charged. 

Several characteristics distinguish the S400 from the S550. The S400 Hybrid makes a different noise, not rougher or louder, merely different. It switches off automatically when coasting or stopped to save fuel, so the tachometer swings to zero. Taking your foot off the brake or touching the gas pedal restarts the engine, and it makes this transition more smoothly than any hybrid we can think of, including pricier V8s. 

Overall, however, the S400 is a bit less smooth than the S550. In places where you're going very slowly, as you might creeping into a tight parking spot, the stop-engine feature may be more active than you'd like, but resting your big toe on the gas pedal to keep the gas engine running will smooth things nicely. The S400's brake pedal also feels more like an on/off switch, because it is, switching the electric motor to a generator that helps slow the car and charge the battery in the process. While the pedal may not be as smooth, the brakes still stop the S400 in short, drama-free, order. 

The V8-powered S550 gets a new engine for 2012. It's 4.7-liter, twin-turbocharged V8 is smaller than the engine it replaces, with highly efficient direct fuel injection. The new engine increase fuel economy 20 percent (projected at 15 mpg city, 23 mpg highway), but it also produces 30 percent more power, with 429 horsepower and 516 pound-feet of torque. The S550 behaves a lot like the S400, except that it delivers substantially more thrust. 

S-Class cars start in second gear to save fuel (unless you've chosen Sport or Manual modes), but even when starting in second gear, the S550 really scoots. Its turbochargers start spinning quickly, delivering viscerally charged, seat-of-the-pants acceleration almost out of character with the S-Class's size and stately demeanor. Mercedes reports 0-60 mph times of 5.4 seconds, and the optional 4MATIC gets the S550 going more easily in poor conditions. 

Every S-Class is library quiet, and virtually free of wind noise at freeway speeds. Normal-volume conversations (with your driving instructor) can be maintained at 130 mph. Road noise increases nominally with the larger-diameter wheels, but the tire noise still won't be heard above a talk-radio program. Engine sounds are more pronounced in the AMG models, but these still cruise in subdued tones. 

Ride quality is superb. The S-Class air suspension combines smoothness with complete control and utter stability as you waft along faster than you think. The suspension can be raised at slow speeds for speed bumps or driveway angles. It automatically lowers at higher speeds for stability and economy, and it can be firmed up in Sport mode if the driver prefers quicker reactions to pillow-gentle manners. 

At any speed, the S-Class duly goes where it's pointed, as we discovered occasionally by accident. The sensation of speed can be muted in this car, but if you find yourself getting into an off-ramp a bit too fast, you'll be impressed by what this 4,500-pound mass can do, even before any electronics come into play to save you from your own poor driving habits. The steering is reasonably fluid, linear, predictable and surprisingly quick for such a long wheelbase. Until you are used to it, the car may turn more than you anticipated given the amount of movement on the steering wheel. 

Some S-Class models speed the turns up by adding a touch of brake to a rear wheel to help rotate the car through the corner. Overall, the brakes are easily modulated and seemingly endless in their ability to shed speed faster the harder you depress the pedal. 

Active Body Control (ABC) adds another element to suspension control by mechanically countering the forces of physics. It forcibly flattens the car's stance through a corner without making the suspension stiffer. It's like a motor race, where the driver swerves back and forth to warm or clean tires while the car appears to lean very little. ABC creates a similar effect in a much heavier, taller, softer riding road car, without wrecking ride quality. 

The Distronic Plus adaptive cruise control option is another S-Class system that works well, even if it takes something like a leap of faith on the driver's part. It uses radar sensors to maintain a pre-set following distance behind the vehicle ahead, and it almost drives the car, working at up to 125 mph and braking to a full stop. 

Set your speed on the freeway (and initially, the size of the gap you prefer to the car ahead), and the S-Class will maintain that speed until it closes on a car directly ahead, in which case it will slow itself to maintain the prescribed gap. If the car ahead speeds up, the S-Class will speed up. If the call ahead slows down, so will the S-Class, on its own, all the way to a complete stop. Or if you change lanes and clear the way ahead, the S-class will accelerate to the set speed. In the typical stop-and-go freeway commute, the S-Class can do all of the braking and accelerating for you. You just do the steering. 

Distronic Plus also enables a feature called Parking Guidance. At low speeds, the system scans available parking spots and shows a 'P' in the dash if the S-Class will fit in a parallel space. When you shift in reverse, the S-class won't back itself into the spot, as some other parking systems do. Rather, it displays a top-view pictogram of the car, showing everything around it, and provides steering guidance. We might like this approach better. 

The S600, with its twin-turbo V12 engine, whirs and hums rather than starts and runs, with a fluidity matched only by more-expensive twelve-cylinder cars. It has a five-speed automatic, but with 510 hp and a prodigious 612 lb-ft of torque (at just 1800 rpm), the S600 does not suffer when it comes to acceleration. The S600 will run 0-60 in less than five seconds with four people on board, as long as you can find traction. The S600 comes standard with 18-inch wheels like lesser S-Class cars, but they are wider in back, with wider tires, to help harness the power. 

The S63 AMG also gets a new engine for 2012: a larger version (5.5 liters) of the S550's twin-turbo V8. It, too, makes more power than the engine it replaces (536 hp, 590 lb-ft), but it's equipped with a start/stop feature like the S400 Hybrid, so it shuts itself off when the car is stopped or idling. The S63 also features a unique seven-speed automatic transmission that works like a conventional clutch-operated manual, without the clutch pedal. These changes improve fuel economy, and the S63 no longer carries a gas-guzzler tax. 

The S63 is a different breed than the S600. It matches the S600 for speed but has crisper, racier response. With its extra-powerful V8 come extra-massive brakes, AMG-calibrated suspension, and 20-inch wheels with ultra-low profile tires. Every component is designed to maintain a torrid pace. The S63 is not the fastest S-Class but it is the most driver-oriented and the most sporting. 

The S65 AMG is a wolf in sheep's clothing, marrying the leather-and-suede luxury of an S600 with the sporting chassis of an S63 and 6-liter twin-turbo V12. It generates 636 horsepower and a staggering 738 lb-ft of torque as smoothly as a jet engine, making your head the nail, the headrest a center-punch and your right foot the hammer. With more torque than just about anything on the road and twice the horsepower of a typical sport sedan, an S65 with traction control off can spin tires through 70 mph, or hit an electronically limited three-miles-per-minute top speed. It will accelerate ferociously from 60 mph to 120 faster than most cars will from a stop to 60, yet it's easily managed if you don't switch the anti-skid electronics off. We found it downright docile when driven moderately. Effortless is a wholly appropriate descriptor here, and maybe excessive. Yet this is the sort of car that makes economically challenged driving enthusiasts dream of winning the lottery, or envious of anyone who can actually afford one. The 2012 SLK350 is legitimately sporty, but it competes with cars that are even sportier, namely the Porsche Boxster and BMW Z4 sDrive35is. 

We drove the 2012 SLK350 on North Carolina's famed Tail of the Dragon and found it to be an ideal car for this technical 11-mile stretch that features some 300 turns. It carved through the corners like an Olympic slalom skier and had just the right amount of power to sprint from one turn to the next. We torture-tested the brakes with two complete turns through the Tail (down and back twice), but they never faded or warped. Most production car brakes would struggle in such conditions. 

With its low stance and short wheelbase, the SLK350 dives readily into turns. When pushed through switchbacks, it rotates nicely, without a tendency to plow forward. It also stays very flat through corners, and gathers itself quickly to head back in the opposite direction. It's a good car for an autocross. 

Just off center, the steering isn't razor sharp, but thanks to its Direct Steer system, it gets much more responsive in tight corners. This variable ratio system becomes quicker the further off center the steering wheel is turned, making it easier to rotate the car through the 180-degree switchbacks found on the Tail of the Dragon. It's a great system, but we still prefer the Porsche Boxster's steering, which is sharper and offers more feedback. 

The SLK-Class structure isn't changed appreciably for 2012, but it didn't really need to be. There is very little cowl shake with the top up or down. The SLK-Class doesn't feel as solid as the Porsche. Ride quality, on the other hand, is more compliant over bumps, making the SLK-Class easier to live with on a daily basis. 

The 2012 SLK350 marks the debut of an all-new engine for Mercedes. Though it displaces the same 3.5 liters as last year's V6, it is more powerful, more responsive and more fuel efficient. Power is available at all speeds with broad rev ranges, so sprinting ahead of traffic and passing will never be a problem. Throttle response is tuned more for comfort than outright performance. It tips in smoothly but doesn't feel dull. The engine note is prevalent, especially at full throttle. It's a raspy, somewhat flatulent note that isn't as cool as a V8 rumble. Still, we thought it fit with the car's sporty character. 

While the SLK350 is quick, it's not as quick as some of its competitors. Zero to 60 mph takes 5.4 seconds in the SLK. The Porsche Boxster S and BMW Z4 sDrive 35is are sub five-second cars. Those looking for more power in the SLK-class will have to wait for the upcoming SLK55 AMG with a reported 415-horsepower 5.5-liter V8. Those who want to save money in the SLK-Class will want to opt for the forthcoming SLK250, which will feature a 201-horsepower turbocharged 1.8-liter four-cylinder. 

The 7-speed automatic works well in everyday driving and aids fuel economy, but it's meant for a passenger car, not a sports car, and we found it lacking for this car. It's one of the major reasons the SLK isn't as sporty as some competitors. When you start to push it during performance driving, shifts in Drive feel slushy. Sport mode holds gears longer to make power more readily available, but the shifts still aren't quick. You can opt to shift it manually via the steering wheel paddles, but it takes its sweet time engaging that next gear. The dual-clutch automated manuals offered by the competition crack off the gear changes much quicker. To compound the issue, Mercedes doesn't offer a manual transmission, which is just wrong for a sports car. 

Summary

The Mercedes Benz S-Class is the baseline when car people talk about true, full-size luxury sedans suited for the daily grind. It comes in several varieties of fast, but only one brand of smooth and granite-solid, all-wheel drive optional. The S-Class is huge inside, with a quiet, coddling interior, an expansive array of mostly useful technology, unparalleled safety systems and a lineup that includes everything from a high-mileage diesel to one of the most powerful four-door production cars in the world. 

New Car Test Drive correspondent G.R. Whale reported from Los Angeles; J.P. Vettraino reported from Detroit. In a class with some impressively sporty competition, the Mercedes-Benz SLK-Class is competitive, but it gives up some performance for a smooth ride, reactions that aren't quite as sharp, and a transmission that fits better in an S-Class than in a sports car. The new engine offers an impressive balance of power and fuel economy, and the looks are more masculine than ever. Prices continue to rise, though, making the SLK350 a less accessible deal than it was in the past. 

Kirk Bell filed this NewCarTestDrive.com report after his test drive of the Mercedes-Benz SLK350 in Tennessee and North Carolina. 

Model Lineup

Mercedes-Benz S350 BlueTEC 4MATIC ($93,425); S400 Hybrid ($92,725); S550 ($95,375); S550 4MATIC ($98,375); S600 ($160,375); S63 AMG ($140,175); S65 AMG ($211,775). Mercedes-Benz SLK350 ($54,800). 

Assembled In

Sindelfingen, Germany. Bremen, Germany. 

Options As Tested

Premium Package ($3,360) includes massaging front seats, Parktronic parking assist and guidance, Keyless Go proximity key, rearview camera; Premium Leather ($2,290) with contrasting stitching ($300); Splitview video monitor ($700); heated steering wheel ($400). Premium Package 1 ($2,590) with heated front seats, AirScarf neck-level heating, Harman Kardon sound system, iPod interface, satellite radio, and remote control for the retractable roof; Multimedia Package ($2,150) with navigation system with voice recognition and real-time traffic information, Mercedes COMAND control screen, SD card reader, and 10-gigabyte music hard drive; Magic Sky Control roof ($2,500).