Back in 1997, a revamped Century hit the showrooms with a bigger, more ergonomic interior and roomier trunk, all wrapped in smooth, flowing sheetmetal that Buick stylists hoped would have a long shelf life. It appears they got their wish. Now four model-years old, today's Century has been growing in popularity each year, proving we shouldn't underestimate the market power of America's senior citizens, rental car companies or business-class road travelers.

The big news this year is the addition of a Special Edition to go along with the well-equipped Custom and the positively pampering Limited versions. According to Century brand manager Anthony Derhake, the Special Edition model was added after Buick figured that "the turn of the century is a great opportunity to celebrate Buick's Century." Marketing aside, the Special Edition wears a monochrome exterior with blacked-out trim and commemorative "2000" badging. Other features include cruise control, a six-way power driver's seat, and an AM/FM cassette player with steering wheel controls. Opt for leather and you'll also get uplevel mirrors, seating and audio.

All 2000-model-year Centurys benefit from a revised 3100 V6 that makes 175 horsepower, up 15 horsepower from 1999, and 195 foot-pounds of torque, or 10 more than last year's engine. The 3.1's new intake and exhaust manifolds not only provide more power, but also increase highway fuel economy by one mile per gallon, to 30 mpg. Century's four-speed automatic transmission has also been improved with electronic controls and a larger torque converter for smoother shifts. Inside, redesigned dual-zone climate controls are now standard on all models. Electronic dual-zone climate control, which replaces slide-and-knob controls with push buttons and LED and digital indicators, is standard in the upper-level Special Edition and optional on the Limited.

Century comes standard with such features as remote keyless entry, automatic power door locks, daytime running lamps with Twilight Sentinel (which automatically controls the headlamps based on lighting conditions), door courtesy lights, battery rundown protection, antilock brakes, traction control, a tire inflation monitor and GM's PASS-Key II theft-deterrent system. OnStar is optional.

Century stacks up well in the high-volume midsize sedan market, where it shows continued sales strength against its domestic rivals. A good safety record and solid build quality makes it an enduring favorite, while gaining ''top buy'' type acclaim from more than a few consumer publications and rating organizations along the way. With the highest customer loyalty rating in the segment, Century buyers seem prepared to stick with this Buick well into the next century.