A haze, oxidation, and corrosion resistant diesel engine lubricant composition, particularly useful in marine and railway diesel engines, contains 0.1-5.0 weight percent of a reaction product additive. The reaction product additive is produced by first reacting substantially equimolar amounts of an anhydride compound which is either a dibasic acid anhydride or isatoic anhydride and a hydrocarbon-substituted mono primary amine or ether amine at a temperature range of 50.degree. C.-150.degree. C. to produce an intermediate reaction product. The intermediate reaction product is thereafter further reacted at an elevated temperature with a substantially equimolar amount of a heterocyclic azole or polyalkylene polyamine compound to form the final reaction product.