Automatic Body Control system is an active, hydraulic suspension system that keeps the car level under acceleration, braking and cornering. Hydraulic cylinders at each corner support a conventional spring and damper, providing adjustments to ride height without intruding on the car's comfortable ride.

Driving the CL on the twisting mountain roads just north of Cannes, the new coupe proved to have very sharp, precise handling. The lack of body roll in corners is uncanny and inspires confidence. The active suspension system could actually let the car lean into curves like a motorcycle, but test drivers found the effect unnerving, according to Mercedes engineers, so the CL maintains an even keel instead.

Charging through the twisties, the antilock brakes, traction control, and electronic stability control systems all worked unobtrusively. The brakes are powerful enough, and the tires grippy enough, that extremely heavy braking is possible without triggering the ABS. We found the brakes easy to modulate and fade free after a lengthy blast through the mountains. The front brakes are ventilated and drilled for better cooling. Brake Assist comes standard to help reduce stopping distances in panic-braking situations, while the ABS allows the driver to maintain steering control.

With the active suspension switched to normal mode the CL's ride is downright plush, and handling is excellent. Switch to sport mode and the CL hones the edge on its handling, and ride suffers so little that no enthusiast is going to care. In sport mode there is less body roll and the car feels more responsive on turn-in. Side-to-side transitions in switchbacks are also better controlled in sport mode.

On the French Autoroute, the CL cruised serenely in the 80-100 mph range. Top speed is electronically limited 155 mph, according to Mercedes.

CL600 accelerates from 0 to 60 mph in less than 6.0 seconds, which edges both the Jaguar XK8 and Aston Martin DB7. CL500 accelerates from 0-60 in 6.1 seconds, while the CL55 AMG performs this in just 5.7 seconds, according to Mercedes-Benz.

On the road, the CL500's aluminum 5.0-liter V8 is as smooth as you'd expect from a Mercedes and feels every bit as strong as its 302-horsepower rating. The V8 left us wondering why anyone would want the CL600's V12.

The answer: more power. The V12 leaves the V8 feeling sluggish in comparison. The CL500 is by no means slow, but the CL600's V12 makes the car feel even faster and even smoother, thanks to the perfect primary balance inherent in V12 and inline 6-cylinder engines.

That means that when the CL600 switches off half its cylinders to save gas, the driver cannot tell, because when running on six cylinders, the CL600's V-12 remains just as smooth. Mercedes-Benz's Active Cylinder Control system in its V12 is nothing like Cadillac's long-ago failed experiment with V-8-6-4, but it does switch off cylinders. When driving in the third, fourth or fifth gear below 3,000 rpm and with the throttle only partly open, the cylinder-control system deactivates the driver's-side bank of cylinders. A computer adjusts ignition timing and throttle position to make the transition seamless. And it works: the driver cannot tell when there are six cylinders running. The benefit is a 20 percent improvement in fuel economy, which lets the CL600 match the CL500's EPA highway rating of 23 mpg.

The five-speed automatic transmission changes ratios imperceptibly. Acceleration comes in a steady rush with no perceptible spikes or flat spots in the torque curve and the transmission seems perfectly matched. However, manual-minded enthusiasts looking for Porsche Tiptronic-like action from the Mercedes Touch Shift will be disappointed. Touch Shift functions like a traditional automatic transmission that is shifted manually. It can be forced to a lower gear, but it continues to shift automatically among the selected gear and lower ones. It will downshift unexpectedly mid-curve, and then won't respond to the request for a manual upshift at full throttle on the ensuing straight. A manual shift option should provide true manual shifting, not automatic shifting with fewer available ratios. The Touch Shift seems pointless because even skilled drivers do just as well to leave the selector in Drive. It seems to be the only flaw in the CL's otherwise apparent perfection.