The Northstar engine is tuned differently for the SLS and STS models: The version used in the SLS produces 275 horsepower at 5600 rpm and 300 foot-pounds of torque at 4000. The engine in the STS delivers 300 horsepower at 6000 and 295 foot-pounds of torque at 4400 rpm. That makes the STS the better choice for drivers who want a high-performance luxury sports sedan and the SLS better for drivers who prefer quietly cruising in luxury. The redline is 6500 rpm in the SLS, 6700 rpm in the STS.

For 2000, the Northstar engine features an all-new head design, new intake manifolds, coil-on-plug ignition and rolling cam runners to reduce friction. Pistons, valves, connecting rods and camshafts were changed or updated. All of this was designed to improve fuel efficiency and reduce emissions. It has also resulted in a quieter engine. Now, instead of having to run 93-octane fuel, the engine burns regular unleaded.

Cadillac's four-speed automatic transmission features a Performance Shift Algorithm that analyzes your driving style and adjusts shifting appropriately. Hammer the throttle and it mimics the crisp shifts of a manual transmission. Accelerate gradually and the transmission shifts smoothly. Go through a corner under hard acceleration and the system is smart enough to delay shifting until you are through the turn for improved handling balance.

Standard on both models is the StabiliTrak system. It uses a special accelerometer to sense even a minor skid. Then, by applying the brakes to individual front wheels and deftly controlling the throttle, it brings the car back under the control-often before you noticed anything was wrong. Seville's steering system is linked to the system's sensors. As a result, steering effort is altered according to how aggressively a driver takes a corner.

For 2000, the third generation of this system raises steering effort in low-traction or emergency-maneuver situations to enhance driver control. Also added this year is side slip-rate control: If the Seville is sliding sideways, both front brakes are momentarily applied to slow the vehicle and allow it to regain stability and lateral traction.

Now add in the Continuously Variable Road Sensing Suspension, a standard feature on all Seville models. The system responds to changing road conditions to optimize ride and handling; it alters shock-damping rates to find an optimal balance between comfort and handling.