The speed-sensitive rack-and-pinion steering gives the S80 a light touch and a steadiness in the curves. In addition to all-wheel drive, the 2.5T AWD comes with Volvo's Dynamic Stability and Traction Control, one of the most sophisticated electronic stability control systems around. If you get the S80 out of shape, it will bring you back in line without drama, often before you even knew you were out of shape. But the ride isn't as smooth in the 2.5T AWD, possibly because of suspension changes that may have been made to accommodate the system. You can feel the sharp bumps on the freeway in a way that you don't feel them in a BMW, Mercedes or Lexus, or in the Volvo S80 T6.

By comparison, the front-wheel-drive T6 offers a smoother ride. The T6 comes with Volvo's new Four-C system (Continuous Controlled Chassis Concept), which monitors speed, acceleration and other dynamic forces and then adjusts the electronically damped hydraulic shock absorbers to provide either optimal comfort or sport control, depending on the position the driver selects on a switch mounted on the center console. The system can adjust the shocks up to 50 times in a single second. In the S80 T6, we found Four-C smoothed out rough railroad tracks and reduced body lean when cornering.

As indicated, we also found the smoother six-cylinder engine a better match for Volvo's flagship luxury sedan than the five-cylinder. In addition to being smoother, it's also more powerful. The T6 is considerably quicker than the 2.5T, although it uses a four-speed automatic compared to the five-speed in the 2.5T. The T6 can accelerate from 0 to 60 mph in less than 6.5 seconds, quicker than a Lexus LS430. It develops 280 pound-feet of torque at just 1800 rpm, and maintains it up to 5000 rpm. More torque at lower revs means stronger power for accelerating away from intersections or making passes on hills. Variable-valve timing enhances the performance of the T6, but the real power comes from its two small turbochargers, which feed three cylinders each. Two small turbos spool up more quickly than one larger unit, delivering maximum thrust at low rpm. As a result, the T6 is quite responsive when cruising at moderate speeds.

The S80's brakes are easy to modulate for smooth stops. Even without Four-C, the suspension does a good job of keeping the S80 level under hard braking: Nosedive during an 80-mph stop was minimal.

The S80 is environmentally correct. The radiator has a special coating that converts up to 75 percent of the ozone it encounters into oxygen.