The effects of engine oil additives on valve train wear

Abstract

AbstractPreventing valve train wear in automotive engines is one of the most important properties of an engine oil. However, the influence of engine oil additives on valve train wear has not been sufficiently clarified.In this investigation, the antiwear performance of additives (such as ashless dispersants, metallic detergents and zinc dithiophosphate ‐ ZDTP) and the influence of the interaction of the additives were evaluated.Secondly, metallic detergents were considered. An overbased calcium sulphonate and an overbased phenate were found to have good anti‐scuffing performance when evaluated in engine tests and in Falex wear tests. However, from the results of four‐ball tests, these additives did not appear to have many extreme pressure properties. From surface analyses, it was determined that a calcium carbonate film was formed on the sliding surface of the Falex test piece, and this film provided good protection against wear.Finally, the interaction of ZDTP, succinimides and calcium detergents and their influence on valve train wear were studied. The decomosition temperature of ZDTP increased with certain additives. including the succinimide. As a result, scuffing was more prone, at temperatures below those increased temperatures. Also, changes in additive concentration on the sliding surface, due to competitive adsorption, altered the antiwear performance of the oil.