Patent ID: 8778854

Claim:
A lubricating composition, comprising: a major amount of an oil of lubricating viscosity and a minor dispersant viscosity modifying amount of: a grafted hydrogenated polymer comprising a polymer backbone and a pendant carbonyl containing group, the polymer backbone comprising at least one of block A and at least one of block B, block A comprising an olefin block, block B comprising a vinyl aromatic block, the mole ratio of monomer units in block A to monomer units in the combination of block A plus block B being in the range from 0.5 to 0.9; substantially all of the pendant carbonyl containing group being grafted on block B, the carbonyl containing group being optionally further substituted to provide an ester, imide and/or amide functionality, the grafting of the pendant carbonyl containing group on block B being conducted by halogenating the vinyl aromatic carbon of block B with a halogenating agent which comprises N-bromosuccinimide and then grafting a carboxylic acid or derivative thereof on the vinyl aromatic carbon in the presence of an activating agent.