1997 Buick Regal Owner's Manual - Page 331

Underbody Maintenance Chemicals used for ice and snow removal and dust control can collecton the underbody. If these are not removed, accelerated corrosion(rust) can occur on the underbody parts such as fuel lines, frame, floor pan and exhaust system even though they have corrosion protection. At least every spring, flush these materials from the underbody with plain water. Clean any areas where mud and other debris can collect. Dirt packed in closed areas of the frame shouldbe loosened before being flushed. Your dealer or an underbody car washing system can do this for you. Chemical Paint Spotting Some weather and atmospheric conditions can create a chemical fallout. Airborne pollutants can fall upon and attack painted surfaces on yourvehicle. This damage cantake two forms: blotchy, ringlet-shaped discolorations, and small irregular dark spots etched into the paint surface. Although no defect in the paint job causes this, Buick will repair, at no charge to the owner, the surfacesof new vehicles damaged by this fallout condition within 12 months or 12,000 miles (20 000 km) of purchase, whichever occurs first.