The 2.5-liter, in-line-5 engine is an oddity in a niche ruled by V-8s, but it's energetic thanks to a turbocharger. It's also smooth at idle. An optional 2.9-liter twin-turbo-charged six-cylinder engine provides an extra 60 hp. To check the intestinal fortitude of the XC90's five-cylinder engine, we hitched up a Ski Nautique on a single-axle trailer. We reached 60 mph in 17.7 seconds with the 4,120-pound payload attached and 9.4 seconds running bareback. The downside with this power approach is a coarse growl when the throttle is down and the engine is straining. However, the five-speed automatic transmission shifted smoothly. The XC90's all-wheel drive mostly relies on the front wheels. At the launch ramp, we noticed some slippage-whether the Dynamic Stability Traction Control button was switched on or off. In spite of a lack of low range, the XC90's low-rpm torque and gear ratio provided ample tugging for towing the rated 5,000 pounds.