Conditions for the laboratory simulation of engine ring and cam-and-tappet wear performance have been established. By using these test conditions, the wear performance of twelve oils of known viscometric properties has been determined. The results suggest that viscosity under either high or low shear conditions is not related to the wear performance under these thin film simulated engine conditions. Wear performance for these oils does appear to be related to the degree of polymer degradation experienced under the conditions of thin film or elastohydrodynamic lubrication.