You can finish work boots in the finest leather, shine them to a high luster and even add nifty little tassels, but no matter what you do, they'll never be dress loafers. They'll still be fancy work shoes. Too fancy, perhaps, to work in. That's the dilemma facing the Mercury Mountaineer. It is, at its core, a truck. It shares its chassis and powertrain options with the upper level Ford Explorer models. The Mountaineer is distinguished from the Ford mostly by fancy trim such as the bright grille, as well as the absence of budget models with basic equipment. If this upscale positioning presents any problems to buyers, it's hardly evident. Though the Mountaineer sells in quantities well short of Explorer's total, it is popular enough that Lincoln-Mercury dealers would revolt if this swank sport-utility were pulled from their lineup. The Mountaineer works well for buyers who want an SUV with some distinction, but can't justify spending $35,000 for a true luxury SUV. For 2000, the interior has been refined for greater comfort and improved appearance. Side-impact air bags have been added to the options list for the front seats. Also optional is a rear load-leveling suspension for 4WD models and a reverse sensing system that uses an ultrasonic sonar system to warn drivers of objects behind the vehicle when backing up.