As mentioned, two engines are available. Both feature Audi's five-valves-per-cylinder technology.

The 1.8T model comes with a 1.8-liter turbocharged 4-cylinder engine that generates 170 horsepower. The engine emits a distant purr that, like the gearbox, conveys a feeling of highly engineered, precision machinery. It revs so freely that it isn't difficult to rev it past the redline and into the rev limiter. The low-pressure turbocharger has a linear power delivery that produces quick acceleration. It develops 166 foot-pounds of torque at just 1950 rpm and that power carries all the way through 5000 rpm, so there isn't any appreciable turbo lag. (Torque is that force that launches you away from intersections and propels you up steep hills.) The 1.8-liter turbo is a great engine, and an excellent choice for enthusiasts who will team it up with the five-speed manual gearbox. It's also an excellent choice for anyone who wants a top-quality, safe sedan that offers a lot of value. The 1.8-liter engine gets about 6 mpg better combined fuel economy than the 2.8-liter V6.

Boasting 190 horsepower, Audi's V6 lends more urgency to forward progress. It's a highly tractable engine with 207 foot-pounds of torque. In other words, it provides the car with instant response when driving around town. Neither you nor the car has to work as hard with this engine as you do with the 1.8-liter turbo. While the V6 isn't a high-revver, it does hustle the Avant down the road in a quicker-than-ordinary hurry, zipping from 0 to 60 mph in less than 7.5 seconds, and 100 mph in 21 seconds. The engine emits a bit more intake noise than we'd like when pressed hard, but in most normal operating conditions we found the interior to be reasonably quiet. The V6 is perfect for those willing to spend a few more dollars for smoother, more relaxed motoring around town and when cruising on the highway. It works better with an automatic than does the 1.8-liter turbo.

Audi's 5-speed manual transmission feels like silk. Taking off from a dead stop and going up through the gears feels seamless to your passengers. The shift action lacks the precision of some of the competition's best gearboxes, however. The optional automatic is a Porsche Tiptronic, which allows drivers to operate it as a semi-manual. It lends a little more variety to automatic driving than the garden variety automatic and can make commuting more entertaining. When left in D, it's an excellent automatic transmission.

This car feels extremely stable. The suspension is firm. Steering is direct and accurate, allowing smooth transitions on winding roads. The A4 provides exceptionally good balance and response in quick side-to-side maneuvers.

The optional Sport Package makes a discernible difference in controlling weight transfer, which lends a significantly higher level of precision to quick changes in direction. The flip side of this is slightly firmer ride quality. The Sport Package makes the A4 more sensitive to tar strips and small bumps than models with the standard suspension setup, but it's a long way from harsh and the tradeoff is worthwhile to enthusiasts for the heightened sense of control. The Sport Package ($750 for 1.8T, $500 for 2.8) lowers the car 20 millimeters and adds slightly stiffer springs, more aggressive shock damping, a thicker rear anti-roll bar, and 16-inch alloy wheels with high-performance P205/55R16 tires along with a leather-wrapped steering wheel. We prefer it. The standard suspension allows just a little too much up and down motion and body roll for this sports sedan and the optional sports suspension offered acceptable ride quality on southeastern Michigan's pothole-infested highways.

Audi's quattro all-wheel drive provides superb grip and lively response in all conditions: wet roads, heavy snow, ice or gravel. The quattro system makes the most of the patchy traction available on wintry roads strewn with sand and occasional icy patches, lending a level of confidence that's rare in any vehicle, whatever the road conditions. Besides adding weather capability, quattro provides tremendous high-speed stability when it's dry.

Braking is smooth and without drama. Augmented by ABS, the four-wheel disc brakes bring the A4 to safe, straight-line stops without the slightest hint of fade in repeated use.