Dispersant/antioxidant VII lubricant additive

A dispersant/antioxidant bound, Viscosity Indeximproving polymethacrylate composition, having a molecular weight ranging from about 20,000 to about 2,500,000, said compositions comprising a base oil and effective amounts of alkyl, methacrylate monomers, a polyunsaturated monomer, an aromatic nitroso compound and, optionally, a dispersant monomer, said composition being prepared by:

• (a) combining a polyunsaturated monomer with (C.sub.1 -C.sub.20) alkyl monomers and (optional) a dispersant monomer, in an oil solvent to provide an intermediate reaction mixture;
• (b) stirring and purging said reaction mixture by nitrogen ebullition at about 200 ml/min. for about 25 to about 35 minutes;
• (c) reducing the nitrogen ebullition to about 20 ml/min.;
• (d) heating the purged mixture to about 70.degree. C. to about 85.degree. C. and adding a radical polymerization catalyst to the purged mixture;
• (e) increasing the temperature of said heated mixture to about 95.degree. -105.degree. C. and maintaining said mixture at such temperature for a sufficient period of time to remove any excess of said polymerization catalyst;
• and
• (f) (optional) recovering the intermediate product polymethacrylate;
• (g) combining said intermediate product polymethacrylate with an aromatic nitroso compound to provide an intermediate reaction mixture;
• (h) stirring said intermediate reaction mixture while purging with nitrogen at a rate of 20 ml/min for about 20 to about 25 min.;
• (i) heating said reaction mixture to about 120.degree. C. and maintaining said temperature for about 30 min.;
• (j) increasing the temperatue of the reaction mixture to about -60.degree. C while collecting water over about 1.0 hour;
• and
• (k) recovering the product polymethacrylate.