The invention comprises a zinc carboxylate-co-ordinated zinc dithiophosphate salt composed of approximately one mol. proportion of zinc carboxylate per mol. proportion of zinc dithiophosphate, said co-ordinated salt being prepared by the method which comprises (1) forming a reaction mixture of one mol. proportion of: (A) a zinc dithiophosphate salt of the formula: FORM:0959115/C2/1 where R is an aryl radical, or an alkyl-substituted aryl radical having from one to 5 alkyl radicals each having from one to 20 carbon atoms, or an alkyl radical containing from 5 to 20 carbon atoms in which the carbon atom adjacent to the carbon atom attached to the oxygen atom in said formula is completely substituted with alkyl groups; (B) at least one mol. proportion, possibly a 10-50% excess, of a zinc salt, of an aliphatic or cycloaliphatic carboxylic acid having from one to 20 carbon atoms or of an aryl carboxylic acid or of an alkyl-substituted aryl carboxylic acid having from one to 5 alkyl groups each containing from one to 20 carbon atoms; (C) water in an amount of at least 0.5 mol. per mol. of zinc dithiophosphate, preferably 10-50 mols. per mol., and (D) a hydrocarbon solvent; (2) heating the reaction mixture to remove the water therefrom by distillation; and (3) filtering the reaction mixture to obtain a solvent solution of the zinc carboxylate-co-ordinated zinc dithiophosphate salt which may be recovered by evaporation of the water and solvent. The products are used as lubricant additives (see Division C5).ALSO:A hydrocarbon lubricating oil composition comprises 0.01 to 10% by weight of a zinc carboxylate-co-ordinated zinc dithiophosphate salt composed of approximately one mol. proportion of zinc carboxylate per mol. proportion of zinc dithiophosphate (for preparation, see Division C2). The zinc dithiophosphate salt has the formula FORM:0959115/C3/1 where R is an aryl radical, or an alkyl-substituted aryl radical having from one to 5 alkyl radicals each having from one to 20 carbon atoms, or an alkyl radical containing from 5 to 20 carbon atoms in which the carbon atom adjacent to the carbon atom attached to the oxygen atom in said formula is completely substituted with alkyl groups. The zinc carboxylate is the zinc salt of an aliphatic or cycloaliphatic carboxylic acid having from one to 20 carbon atoms or of an aryl carboxylic acid or of an alkyl-substituted aryl carboxylic acid having from one to 5 alkyl groups each containing from one to 20 carbon atoms. The composition may be in the form of a concentrate.
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