1995 GMC Sonoma Owner's Manual - Page 273

Underbody Maintenance Chemicals used for ice and snow removal and dust control can collect on the underbody. If these are not removed, accelerated corrosion (rust) can and occur on the underbody parts such as fuellines, frame, floor pan, exhaust system eventhough 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 should be loosened before being flushed. Your dealer or an underbody vehicle washing system can do this for you. Chemical Paint Spotting Some weather and atmospheric conditionscan create a chemical fallout. Airborne pollutants canfall upon and attackpainted surfaces on your vehicle. This damage can take 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, GMwill repair, at no charge to the owner, the surfaces new vehicles damaged by this fallout condition of within 12 months or 12,000 miles (20 000 km) of purchase, whichever comes first. This applies only to materials manufactured and sold by General Motors. Bodies, body conversionsor equipment not made or soldby General Motors are not covered. 6-55