For 2010, the Audi S4 sport sedan switches out its hunky V8 engine for an equally powerful yet more fuel-efficient supercharged V6. In addition, the S4 receives a new optional transmission and a new optional Sports Rear Differential for 2010, as well as a number of new interior features borrowed from the Audi A4, which received a full redesign in '09.

The S4's 3.0-liter, direct-injection TFSI supercharged V6 provides faster acceleration than the V8 it replaces, thanks to its 325 lb-ft of torque, compared to the V8's 302 lb-ft. Horsepower for the V6 checks in at 333, a slight drop from the V8's 340 hp. However, fuel economy for the V6 improves dramatically, to 18/27 mpg when mated to a six-speed manual transmission, compared to the V8's 14/21 mpg. The new V6 pushes the S4 from 0-60 in 4.9 seconds.

The S4 comes standard with a manual transmission, but owners can opt for a new seven-speed S tronic automatic transmission. It provides rapid, precise shifts, which help improve acceleration. In addition, drivers can shift manually using either the shift lever or steering-wheel-mounted paddle shifters.

The new powerplant works in conjunction with Audi's all-wheel-drive quattro system, which comes standard on the S4. Under normal driving conditions, the quattro system defaults to a rear bias, with a 40/60 front/rear torque split. However, when required, the system automatically transfers power away from spinning wheels to those with sufficient grip as needed to ensure maximum traction and stability on all types of road surfaces. Owners can add the optional Sports Rear Differential for 2010, enhancing the S4's already highly capable agility and control.

Although previously available as a cabriolet, the S4 comes only as a sedan for 2010. Outside, it displays a sleek, powerful exterior appearance, with new front and rear S-type bumpers, a subtle rear spoiler, new LED taillights, and chrome quad tailpipes. Other exterior design cues include the distinctive Audi deep-mouthed grille with vertical chrome bars, eyebrow-shaped bi-xenon high-intensity headlights, aluminum optic mirrors, and high-performance 18-inch tires with S-style five-spoke wheels.

Inside, owners will find an upscale, well-equipped cabin with plenty of interior room, thanks to the S4's stretched wheelbase for 2010. Audi equips the sedan with such S4-specific features as heated power-adjustable sport front seats with unique colors, a black interior headliner, and brushed-aluminum interior trim with optional wood, carbon fiber, or stainless steel trim. The leather-wrapped steering wheel, aluminum door-sill inlays, key fob, and gauge cluster display S4 badging. Three-zone automatic climate control also comes with the standard package.

In addition, Audi offers the S4 with a new third-generation version of its MMI (Multimedia Interface), which makes it easier for drivers to manage the sedan's audio, climate control, and navigation systems, as well as other interior and exterior systems, thanks to a revamped interface with revised control logic. The base S4 comes equipped with the second-generation version of the MMI, while the newly updated version with navigation comes standard with the S4's optional Prestige package. Other standard tech-related features for the S4 include Bluetooth, electronic cruise control, a 180-watt Audi Concert audio system with a CD player and Sirius satellite radio, and a music interface, which enables full iPod integration with the MMI system.

Safety equipment includes Audi's Electronic Stabilization Program. Sideguard head-protection airbags come standard, while rear side airbags for second-row passengers remain an option for 2010.