The Audi A4/S4 is a midsize sedan and wagon designed to compete in the same segment as the BMW 3 Series and Mercedes-Benz C-Class. Originally introduced in the early '90s as a replacement to the Audi 80/90 family, the A4 is now in its third generation (last redesigned for the 2006 model year). The A4/S4 is available in both 4-door sedan and "Avant" (5-door wagon) variants. The sedan is offered with a standard 2.0-liter, turbocharged 4-cylinder engine with a choice of front-wheel drive or Audi's "Quattro" all-wheel drive.
The high-performance S4 model features a supercharged V-6 engine with a standard Quattro drivetrain. In addition to its larger engine, the S4 includes upgraded suspension, wheels, brakes, and a sportier interior. The Avant, or wagon, variant is only offered with the 2.0-liter turbocharged engine and standard Quattro driveline. After making several changes to its A4 lineup for the 2010 model year, the automaker is leaving it relatively unchanged for 2011.