The Influence of Polymer Additives on Valve Train Wear

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Abstract
Valve train wear tests were conducted to evaluate the effect of polymeric thickeners on wear for oils containing no antiwear additives. The presence of polymer additives causes an increase in wear compared to hose oil having a lower viscosity. A higher molecular weight polymethacrylate with less elastohydrodynamic film forming capability gives rise to less valve train wear. Furthermore, the amount of valve train wear increases with an increase in polymer concentration in gravis per liter. Consequently, the most important parameters for valve train wear turns out to be the quantity of polymer molecules per unit oil volume. The increase in wear due to the presence of polymer was also observed in four-ball wear tests carried out at low speed and high load. It is observed that the valve train wear trend has a good correlation with four-ball wear tests under low speed and high load conditions for various polymer-thickened oils. The correlation of the two test methods may be an indication that the same mechanism is causing the increase in wear.