Today most instrument panels and interior padded parts are made of polyurethane foam covered with a polyvinyl chloride (PVC) skin. A key concern in the industry is the long-term appearance of the interior parts. Recent automotive designs have resulted in more pronounced windshield angles and increased surface areas of the instrument panel exposed to direct sunlight. A consequence of these design features is closed car interior temperatures approaching 250°F (1) (120°C). The resulting thermal and light stress causes many instrument panels to discolor and crack.Previous studies have shown that vinyl staining is the result of dehydrochlorination of the PVC which is manifested as color changes as well as cross-linking of PVC, and foam degradation.In this study, the results of heat aging tests at 300°F (149°C) indicate that colorimetric testing is a reliable and objective method of monitoring stain development. Using this procedure, it was seen that different catalysts in urethane foam formulations can dramatically affect the staining characteristics of vinyl surfaces.