The 2008 STS is a 4-door, 5-passenger luxury sedan, or luxury sports sedan, available in 6 trims, ranging from the V6 to the V8 Premium Luxury Performance.Upon introduction, the V6 is equipped with a standard 3.6-liter, V6, 302-horsepower engine. The V8 Premium Luxury Performance is equipped with a standard 4.6-liter, V8, 320-horsepower engine. A 6-speed automatic transmission with overdrive is standard on both trims.