The Determination of Additive Effects in a Japanese Valve Train Wear Test Using an Orthogonal Statistical Design

The factors affecting valve train wear such as individual additives, additive interactions and engine variability have been investigated using an orthogonal type of statistical experimental design. 27 oils formulated on the basis of a 5-factor {Zinc dialkyl dithiophosphate (ZnDTP), dispersant, detergent, Viscosity Index (VI) improver and engine}, 3-level (3 types of each additive) array were used to assess the significance of each factor and possible interactions between ZnDTP and other additives on cam and rocker arm wear in the Toyota 20R test. ZnDTPs had the most significant effect followed by dispersant, detergent and VI improver. Additive interactions were also detected and hence using this experimental design novel additive combinations giving good performance can be identified and used by the lubricant formulator.