The 2009 Cadillac STS is available in two primary models designated by their type of engine: V6 or V8. The V6 model is powered by a direct-injected 3.6L DOHC V6, making 302 hp and 272 ft-lb of torque. Direct injection allows for an increase in power without a drop in fuel efficiency. The V8 model is powered by a 320-hp, 4.6L Northstar V8 engine. A 6-speed automatic transmission is offered throughout the model range, and its steep first-gear ratio enables especially strong off-the-line performance.

Both models can be specified with an all-wheel drive system for improved all-weather stability and traction, but there's also a sophisticated standard StabiliTrak electronic stability control system that helps restore stability. In all-wheel-drive V8 models, StabiliTrak has a special front-wheel steer feature in which the system will use a steering motor to turn the front wheels into a skid when the rear wheels lose traction in order to more quickly restore control.

The STS offers several leading-technology options. Most notably, a Lane Departure Warning system, which monitors lane marking and warns the driver when the vehicle drifts out of its lane, and a Side Blind Zone Alert System, which uses radar beams to scan the lanes adjacent (about 11 feet on both sides and about 16 feet rearward) and flashes an indicator light when the space is occupied. Another standout feature is the Intellibeam automatic high-beam system available on the V8, which automatically switches between high and low beam headlights based on the distance of oncoming traffic.

The top-option "infotainment" system on the STS has 15 Bose speakers, a 6-disc, MP3-compatible CD/DVD changer, an 8-inch screen, and an advanced navigation system, plus Bluetooth hands-free capability and voice recognition. Bluetooth hands-free telephone interface is also available on STS models not equipped with the above system.

The STS Platinum Edition is available in either model and has a distinctive look and feel, with 18-inch chrome wheels, a brighter grille, and an exclusive exterior finish, plus a hand-cut, sewn, and wrapped instrument panel and door trim, Tuscany leather seats, olive ash burl wood and chrome accents, a heated leather-wrapped steering wheel, and new alcantara headliner.

At the top of the STS range stands the limited-edition STS-V, a high-performance version of the STS. It carries a 469-hp, 4.4L supercharged version of the Northstar V8, huge Brembo disc brakes, larger wheels and tires, larger front and rear stabilizer bars, and unique exterior trim. The STS-V's engine is hand-built by a single craftsman from start to finish. Inside, it also gets leather-wrapped surfaces throughout, plus olive ash burl wood trim and aluminum accents. According to GM, the STS-V can accelerate to 60 mph in less than six seconds.;