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.
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.
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.
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.
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.
|Model||2012 Mercedes-Benz CLS-class|
|Power train||Twin turbocharged direct-injection 4.6-liter V-8, 7-speed automatic transmission|
|EPA fuel economy||17 mpg city/26 mpg highway|
|Observed fuel economy||22.3 mpg|
|Navigation||Hard-drive-based with traffic|
|Bluetooth phone support||Yes, with contact list|
|Disc player||MP3-compatible six-CD/DVD|
|MP3 player support||iPod integration|
|Other digital audio||Onboard hard drive, Bluetooth audio streaming, USB drive, satellite radio, HD Radio|
|Audio system||Harman Kardon 14-speaker surround-sound system|
|Driver aids||Adaptive cruise control, lane departure warning, lane departure prevention, blind-spot detection, rearview camera|
|Price as tested||$82,765|