Some Effects of Zinc Dithiophosphates and Detergents on Controlling Engine Wear

The modern crankcase oil should prevent wear in both gasoline and diesel engines. This paper addresses the effects of zinc dithiophosphates (ZnDTP) and detergents on wear control in both applications. The authors find a need to properly balance detergent and ZnDTP types in order to obtain optimum wear performance for gasoline valve train wear. In addition, high levels of magnesium sulfonate produce higher bore polishing and/or ring wear than calcium detergents in three different diesel engine tests. Finally, a proper balance of sulfur-containing components and ZnDTP is necessary to prevent corrosive attack of the bronze pins in some diesel camshaft roller followers. Film and metallurgical analyses of used engine test parts are presented.