The S80 engines are the first transversely mounted inline 6-cylinder engines in modern times. The engine hums when it's working, very lightly and muted. You can scarcely hear it, even when pulling steadily uphill at 80 mph with good momentum. Wind noise and tire noise are heard as much as the engine; there isn't much of it, but it can be heard because the engine is so quiet. You don't hear the engine at all when the transmission downshifts. All you see is the upward twitch of the tachometer needle.

The power produced by the basic 2.9-liter inline six seems on the light side for a luxury car. It's a bit sluggish off the line. It's also noticeable when traveling with a heavy load. We took a 200-mile trip in the 2.9 sedan with four adults and a heavily loaded trunk, and, not unexpectedly, the engine definitely noticed the difference. Its 207 pounds-feet of torque developed at 4200 rpm aren't enough on long grades, particularly at higher altitudes, and the 197 horsepower isn't fully developed until 6000 rpm.

The T6 model is at the other end of the performance spectrum. Mash the throttle and the response is instantaneous. Its small twin turbochargers spool up quickly to develop maximum power at low rpm: 280 pounds-feet of torque at just 2100 rpm (and 268 horsepower at 5400 rpm). As a result, the T6 is quite responsive when cruising at moderate speeds, say 25-50 mph. And there's easily enough power to light up the front wheels. Volvo's traction control system steps in to ensure the front tires only momentarily lose grip, unless you've pressed the STC button to turn it off, that is.

The ride is comfortable, and the suspension takes bumps well, eliminating road imperfections. The S80 handled our full load very well. The luxury-tuned suspension, maybe combined with the front-wheel drive and steering geometry, allows the car to move around on the road a bit, however. Coupled with a vague spot at the center of the steering, the S80 wanders ever so slightly, requiring small steering corrections. In Volvo tradition, the steering is a bit on the slow side, demanding more steering input than other cars in this class. Overall, the S80 doesn't have the handling precision and poise of the BMW 5 Series and some of the other cars in this class.

The brakes are adequate, although the pedal feel isn't particularly sensitive. The suspension does a good job of keeping the S80 level under hard braking: Nose dive during a hard application of the brakes at 80 mph was minimal.

The four-speed automatic transmission shifts smoothly and precisely, most notably at higher loads. But occasionally at lower speeds, a quick stomp on the gas causes it to trip over itself on downshifts. The momentary bog creates a slight response delay and lurch of the car once the downshift takes place.