Dispersant, VI improver and antioxidant additive, and lubricating oil composition containing same

A lubricating oil composition comprising a major amount of an oil of lubricating viscosity and a minor amount effective to impart viscosity index improvement, dispersancy, and antioxidant properties to said oil of an additive reaction product prepared by the steps comprising:

• (A) reacting a copolymer, selected from the group consisting of ethylene copolymers prepared from ethylene and at least one C.sub.3 -C.sub.10 alpha-monoolefin and, optionally, a non-conjugated diene and triene, and block copolymers prepared from styrene and a diene monomer having from 4 to 6 carbon atoms, said copolymer having a number average molecular weight ranging from about 25,000 to 300,000, with at least one olefinic carboxylic acid acylating agent to form one or more acylating reaction intermediates characterized by having a carboxylic acid acylating function in their structure;
• (B) reacting said reaction intermediate in (A) with an unsaturated hydrocarbyl amine represented by the formula:
• RNH.sub.2
• in which R is an unsaturated hydrocarbyl radical having from 3 to 24 carbon atoms to form an imide reaction product;
• and
• (C) reacting said reaction product in (B) with a nitroso compound represented by the formula:
• R--N.dbd.O
• in which R is an aromatic hydrocarbon radical or aromatic amine radical having from 12 to 20 carbon atoms.