TRIBOLOGICAL PROFILE OF ENVIRONMENTALLY ACCEPTABLE LUBRICANTS FOR PASSENGER CAR SHOCK ABSORBERS
Due to several restrictions, substances for environmentally friendly and biodegradable lubricants getting more in focus of passenger car OEMs and suppliers R&D activities. Goal of the present investigation is to characterize the tribological performance of different shock absorber fluids, including those declared as environmentally acceptable lubricants. Therefore, six lubricants differing in their base oil were tested under laboratory conditions, in bench tests and finally in vehicle tests. The oils tested are composed of Group I- and Group III-mineral base fluids and two synthetic Group V base stocks (one classified as readily biodegradable), formulated with standard additives for shock absorbers. Friction properties under oscillating sliding conditions and Stribeck-curves were determined besides damping force in real applications. Subjective car evaluation on gave good conclusions how the oil and its tribological properties can influence the driving performance.