The best deal is the base five-cylinder engine with the five-speed automatic. Volvo's 2.5-liter five-cylinder produces 208 horsepower and 236 pound-feet of torque at 4500 rpm. We found it delivered plenty of power for the real world, and the 24-mpg EPA Highway rating is excellent for that much power in a vehicle as heavy as the XC90. But what makes the five-cylinder engine especially sweet is the five-speed automatic that comes with it. It's a responsive transmission. Stand on the gas while cruising along on the highway and it quickly downshifts from fifth to third gear and XC90 eagerly zooms away. The five-cylinder engine doesn't seem to have a lot of torque at low engine speeds (1500 rpm), but the responsiveness and flexibility of the five-speed transmission makes good use of the engine's power. The transmission includes a manual-shift feature called Geartronic.

The T6 model comes with a more powerful six-cylinder engine, but its transmission is only a four-speed. The T6 transmission must handle a lot more torque, and a beefed up five-speed automatic wouldn't fit in the engine compartment with the bigger engine. The heavier four-speed automatic shifts more slowly and less smoothly than the 2.5's five-speed. Nor is the six-cylinder engine as smooth or as quiet as the five-cylinder. There was a distinct engine vibration between 45 and 50 mph in third gear, at about 2000 rpm. And although 268 horsepower and twin turbos sounds hot, we weren't impressed. With the four-speed, the engine sometimes feels like it's working hard, and the T6's lower mileage rating means about 60 fewer miles per tank.

Volvo developed the V8 for the U.S. where 30 percent of all SUVs are sold with V8 engines. Because Volvo has no history with V8s, it turned to Yamaha, which has a good relationship with Volvo's parent company, Ford, to develop a new engine compact enough to fit in the XC90's engine bay. Volvo linked the V8 to a six-speed automatic to make the best use of the engine's torque curve, which reaches 271 pound-feet of pulling power at just 2000 rpm. Volvo also made some changes in its all-wheel-drive system to send more power to the rear wheels for better take off from a standing start. We spent several hours in the V8 and found it well suited to the sort of driving done by many American SUV owners. We stayed on pavement, enjoyed quick acceleration and sure-footed passing maneuvers.

Regardless of engine, we were impressed with how silky smooth the XC90 feels at 80 mph. Its chassis closely follows the design of the V70 wagon, but is wider and the components are beefier. It handles bumpy roads with dips and gullies well without bottoming when driven hard. The XC90 doesn't offer the sporty handling of a BMW X5 or Infiniti FX35. Its power rack-and-pinion steering is on the heavy side, and not as quick in the really tight stuff. But it feels reasonably tight in general, with decent feedback to let you know how the front tires are gripping. There's minimal body sway under hard cornering. The DSTC electronic stability control stepped in a few times when we were thrashing down a particularly ornery road, and the system applied the brakes at one wheel without cutting the throttle, although we aren't sure if it was the gyroscopic roll sensor or traction sensors that triggered its operation.

The ride quality in the XC90 is very good, stiff at the wheels, but not in the cabin. It didn't exactly absorb the ridges and bumps, because you could feel the suspension working over them; but it didn't transfer any harshness to the arms or seat of the pants at all. Speed bumps in particular were interesting; it was as if the suspension challenged them and hammered back, protecting us from jouncing even when we hit them at 15 mph.

The all-wheel-drive system is effective, too. It operates seamlessly, and the driver will almost never know when it's working. In normal, good-traction conditions, 95 percent of the engine's power goes to the front wheels. If the front wheels lose traction, a multi-plate clutch begins routing power to the rear, to a maximum split of 65 percent to the back tires. This frontward bias leaves the XC90 with a default understeer condition, or a sliding at the front tires near the limits of handling. This push is much easier to handle than a skittish rear end, because a driver's natural instinct is to slow down, and that basically solves the problem.

The six-cylinder T6 has stiffer front springs than does the five-cylinder XC90 (to handle the heavier engine), and speed-sensitive steering. These are supposed to give it more of a true high-performance feel. To some extent they do, but mostly they detract from the XC90's overall balance and introduce some mildly annoying handling characteristics. Unless you need the bragging rights of a six-cylinder engine, we highly recommend the XC90 with the standard five-cylinder engine.