Abstract: There is provided a lubricating oil composition for use in medium speed diesel engines, such as railroad locomotive diesel engines. This lubricating oil composition comprises an oil of lubricating viscosity and a minor amount of a reaction product that is obtained by reacting an alkyl-substituted dicarboxylic acid compound selected from the group consisting of alkyl-substituted dicarboxyic acids, alkyl-substituted dicarboxylic acid anhydrides, and mixtures thereof with a basic salt of aminoguanidine under selected conditions that will provide a product rich in alkyl bis-3-amino-1,2,4-triazole.

Abstract: Silver protective lubricant compositions essentially free of chlorine and zinc-containing compounds comprise a 1,3,4-thiadiazole, an overbased detergent and an ashless dispersant. The invention is also directed to a method of silver protection in engines which utilizes the above lubricant composition.

Abstract: Overbased sulfurized phenates formed by the process comprising contacting at reaction conditions a composition comprising a phenolic compound, sulfur and an alkaline earth metal base selected from the group consisting of calcium, barium, magnesium, and strontium, in an amount insufficient to fully react with the phenolic compound, and contacting the above intermediate composition with an additional amount of alkaline earth metal base and carbon dioxide, wherein the molar ratio of carbon dioxide absorbed to overbasing alkaline earth metal is from about 0.70 to about 0.95.