2012 Mercedes-Benz CLS550 review:

2012 Mercedes-Benz CLS550

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Starting at $71,300
  • Available Engine Gas
  • Body style Sedan

Roadshow Editors' Rating

8.4 Overall
  • Cabin tech 9
  • Performance tech 8
  • Design 8
Aug 2011

The Good The standard air suspension in the 2012 Mercedes-Benz CLS550 delivers a very comfortable ride, and the Harman Kardon audio system reproduces music with excellent fidelity. Adaptive cruise control, blind-spot detection, and lane departure systems all work very well.

The Bad The engine creates uneven acceleration in certain power bands.

The Bottom Line Mercedes-Benz bolsters its reputation for luxury with the 2012 CLS550. A powerful and efficient engine propels this sleek ride, and there are a number of advanced driver-assistance features.


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2012 Mercedes-Benz CLS550

The 2012 Mercedes-Benz CLS550 is one of the sleekest car designs on the road. You might mistake it for a big drop of liquid mercury flowing down the highway. Mercedes-Benz did an excellent job maintaining a low, nicely curved roof and molding the rear fenders into its sides. If you don't want people stopping to admire your car, the CLS550 is not for you.

As an update of one of Mercedes-Benz's big sedans, the CLS550 sports a new engine making its way down the lineup of all Mercedes-Benz 550-designated cars, a direct-injection V-8 with twin turbos. This engine, and a new seven-speed automatic, combine for surprisingly good fuel economy. The car also comes standard with an air suspension, giving it one of the most comfortable rides around.

Mercedes-Benz has done a lot of work on driver assistance electronics, and the CLS550 serves as a showcase for these innovative technologies. The cabin tech suite features very good navigation and stereo, but in this area the company doesn't push the envelope. Mercedes-Benz shies away from the kind of application integration currently coming into vogue.

Luxury ride, sound
Two things make the CLS550 a luxury ride par excellence: its air suspension and the Harman Kardon 14-speaker surround-sound system. Although it's over $70 grand, you won't find a car at this price with a better ride. Bumps and rough asphalt are beneath the notice of the CLS550. If the princess who famously felt a pea underneath 20 mattresses were to ride in the CLS550, she would drift off into a deep sleep.

The CLS550 does not lack for audio sources.

Add to that extremely comfortable ride the beautifully detailed music produced by the Harman Kardon audio system. From its speakers, you can easily hear every percussive snap and guitar string strum. Horns and vocals come through with incredibly rich quality. High notes from this system can get too shrill, and sustained trumpet notes can become painful. Bass, however, is very well-controlled.

The stereo allows about every audio source you could want. Mercedes-Benz adds Bluetooth audio streaming to its roster, which also includes iPod integration, the car's own hard drive, and HD Radio. There is even a PC card slot, an odd little anachronism. But Mercedes-Benz has not jumped on the app bandwagon yet, so there is no Pandora or Internet radio integration.

At this level of luxury, heated and cooled power seats with memory settings are, of course, standard. And available for the driver is a massage seat with active bolstering. This massage function uses air pockets in the seat, which are not as effective as rollers, but still quite decadent.

Adaptive cruise control matches the speed of slower traffic ahead.

Further enhancing the driving experience is a nice set of assistance features. Mercedes-Benz for some time has offered adaptive cruise control, which adjusts the car's speed to match that of traffic ahead. This system works very well, letting you drive for many miles in light to moderate traffic without touching the gas or brake pedals. We have even seen it bring the car to a complete stop as traffic ahead stopped.

A blind-spot detection feature lights up a red triangle in the side mirrors, to warn of cars to the sides of the CLS550. That triangle flashes and a warning tone sounds if you activate the turn signal. In the CLS550 Mercedes-Benz also offers its night vision feature, which turns the instrument cluster into a longer view of the road ahead than you can see unaided.

And new for the CLS550 is a lane departure warning and drift prevention system. This system tracks the lane lines, showing an icon in the instrument cluster when it is active. If you drift over a lane line without signaling or actively steering, it vibrates the wheel and sounds a warning tone. Continue to drift and it slightly brakes the offside wheels, causing the car to arrest the drift. When it activates, it feels as if the car is quickly rotating back into the lane, with enough movement to wake up dozing drivers.

Optional LED headlights follow the angle of the steering wheel.

CNET's car came equipped with LED headlights, part of a $4,390 package that also includes an iPod interface. These headlights projected well-defined bright beams similar to HID headlights. They track with the steering angle, lighting up corners.

Turbo lag
The CLS550's air suspension can be switched to Sport mode, which stiffens the suspension a bit. But the car still feels heavy and leans in hard cornering. The air suspension is not as good for sport driving as magnetic suspension systems, which can constantly adjust the stiffness at each wheel in response to the road and driving conditions.

This new engine is very efficient.

The new engine uses a variety of efficiency technologies to maintain power and deliver reasonable, if not stellar, fuel economy. Direct injection sprays fuel into the CLS550's eight cylinders, ensuring a more complete burn. Twin turbochargers let Mercedes-Benz get away with 4.6 liters of displacement, with the engine still producing 402 horsepower and 443 pound-feet of torque.

Mercedes-Benz says that engine gets the CLS550 to 60 mph in just 5.1 seconds, while earning an EPA fuel economy rating of 17 mpg city and 26 mpg highway. In CNET's testing over a variety of roads, the car came in at 22.3 mpg, in the middle of that range, an impressive feat considering Mercedes-Benz's older 5.5-liter V-8 tended to come in closer to 17 mpg average.

You can definitely feel the power from this engine, but it often comes on unevenly, probably due to turbo lag. At a quarter to midthrottle, the car has a tendency to lunge, which can be uncomfortable in urban environments. Very moderate throttle from a start is adequate to keep up with traffic and leads to smoother acceleration.

On the upper end, while torturing the car on mountain roads we found that maintaining an engine speed around 5,000rpm led to massive power on tap. The CLS550 comes with a seven-speed transmission with Economy, Sport, and Manual modes. The Sport mode is not very aggressive, letting the engine drop down to its 1,500rpm cruising speed.

The Mercedes-Benz drive selector takes getting used to, but is perfectly adequate.

Use Manual mode to keep it in second or third gear and the engine speed keeps the turbos spooled up. The throttle becomes a precision control, and the car maintains linear acceleration. But the engine offers so much power that third gear at 5,000rpm definitely puts you north of 60 mph. Fourth gear would be out of the question on anything short of a long, mostly straight road.

The seven-speed automatic transmission is a new one for Mercedes-Benz. It features a lock-up clutch to eliminate the inefficiency of a torque converter. But this transmission doesn't have the hard gear changes of a dual-clutch transmission. It shifts smoothly, whether in Automatic or Manual modes.

3D navigation
When it comes to the navigation system, Mercedes-Benz doesn't mess around with options. This hard-drive-based system with maps featuring traffic and 3D-rendered buildings comes standard in the CLS550. Route guidance can dynamically avoid traffic problems, and shows helpful information such as which lanes you should be in for upcoming turns.

The navigation system renders the buildings of downtown San Francisco in 3D.

Mercedes-Benz's familiar COMAND system controls all of the cabin tech functions. It is an indirect controller, with a big dial on the console and buttons for direct access to navigation, the stereo, and the phone system on the center stack. The car also comes with an adequate voice command system, which lets you place calls by name through a Bluetooth paired phone.

The instrument cluster also serves as an auxiliary cabin tech controller, letting the driver use buttons on the steering wheel to view trip, navigation, audio, and phone information in a display on the speedometer.

In sum
The 2012 Mercedes-Benz CLS550 sports systems that shoulder some of the driving burden, especially for long highway cruises, appropriate for a luxury car. These driver assistance features also bring in a substantial safety element. Available LED headlights are also a nice touch. The cabin tech suite is pretty standard among the German luxury set these days, but the audio system earns the car an extra bump in its tech rating.

Engine, transmission, and suspension are all excellent high-tech features of the CLS550, but with one caveat: Mercedes-Benz needs to smooth out the power delivery to prevent the uncomfortable lunges from this car. Other than the acceleration issue, the CLS550 ends up delivering a very smooth ride, but don't expect to take this cruiser out to track days.

Tech specs
Model2012 Mercedes-Benz CLS-class
TrimCLS550
Power trainTwin turbocharged direct-injection 4.6-liter V-8, 7-speed automatic transmission
EPA fuel economy17 mpg city/26 mpg highway
Observed fuel economy22.3 mpg
NavigationHard-drive-based with traffic
Bluetooth phone supportYes, with contact list
Disc playerMP3-compatible six-CD/DVD
MP3 player supportiPod integration
Other digital audioOnboard hard drive, Bluetooth audio streaming, USB drive, satellite radio, HD Radio
Audio systemHarman Kardon 14-speaker surround-sound system
Driver aidsAdaptive cruise control, lane departure warning, lane departure prevention, blind-spot detection, rearview camera
Base price$71,300
Price as tested$82,765

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