Reduction in vehicle weight is a key goal for today's automobile design. This is being accomplished, in part, by replacement of metal components with lighter weight, multifunctional engineering plastics and composites.Additional weight reduction potential exists, however, through the use of high performance plastic parts from aramid and polyimide resins. The weight reducing value attributable to parts from these materials emanates from their high performance properties, and not necessarily their light weight. Superior properties allow the aramid and polyimide parts to be used in applications involving bearing loads, moving contact speeds and temperatures found too severe for other plastics. The principal benefit of their use is the designer's ability to downsize companion metal parts and to more readily incorporate lightweight metals such as aluminum.This paper describes application and design concept areas where high performance plastic parts can contribute to achievement of improved functionality at a cost-benefit level consistent with automotive requirements. Physical properties important to engineering design, such as, strength, creep resistance, thermal expansion, wear life (in both lubricated and dry systems) and frictional characteristics are highlighted.