Valve train wear performance of crankcase oils and their components has been evaluated in 20-hour Volvo 2 litre engine tests. Results show that specifying a minimum zinc level in an oil does not necessarily assure freedom from cam and tappet wear. The interference effect of the detergent inhibitor package (DI) on the functioning of the anti-wear additive is clearly demonstrated. Case studies of lubricants at performance levels ranging from API SC-CB to SE and CD highlighted the effects of viscosity index improvers (VII) oil quality variation, tappet surface treatment, effectiveness of various zinc dialkyldithiophosphate agents (ZDDP) and failure mechanisms. Test procedure investigations were conducted to evaluate the precision of the method, the effect of cycle time on the failure rate and test engine life.