A process for preparing a lubricating composition comprising preparing a polymer by a process comprising the steps of,, optionally, and: contacting: (i) a free radical initiator; (ii) a chain transfer agent containing a thiocarbonyl thio group and a free radical leaving group; and (iii) a radically polymerisable monomer, to form a polymer chain; wherein the process of step is a controlled radical polymerisation process with living characteristics; and at least 50 % of the polymer chains from step contain a reactive end group capable of reacting with a polyvalent coupling agent; and contacting the polymer prepared by step with a polyvalent coupling agent to form a star-polymer, wherein the star polymer is a block-arm star polymer, wherein the block-arm star polymer contains a polymer arm derived from two or more monomers where the monomers are on the same arm, and wherein the star polymer is derived from at least two monomers comprising: (a) at least 50 wt% of a C12 to C15 alkyl substituted (meth)acrylate monomer; and (b) less than 50 wt% of an alkyl (meth)acrylate monomer containing 1 to 30 carbon atoms other than the C12 to C15 alkyl (meth)acrylate monomer; and (c) optionally containing less than 20 wt% styrene; and (d) optionally containing less than 10 wt% alkyl methacrylamide; optionally contacting the polymer prepared by step or step with a polymerisation inhibitor; and mixing the polymer prepared by step or step with an oil of lubricating viscosity to form a lubricating composition. contacting: (i) a free radical initiator; (ii) a chain transfer agent containing a thiocarbonyl thio group and a free radical leaving group; and (iii) a radically polymerisable monomer, to form a polymer chain; wherein the process of step is a controlled radical polymerisation process with living characteristics; and at least 50 % of the polymer chains from step contain a reactive end group capable of reacting with a polyvalent coupling agent; and (i) a free radical initiator; (ii) a chain transfer agent containing a thiocarbonyl thio group and a free radical leaving group; and (iii) a radically polymerisable monomer, to form a polymer chain; contacting the polymer prepared by step with a polyvalent coupling agent to form a star-polymer, wherein the star polymer is a block-arm star polymer, wherein the block-arm star polymer contains a polymer arm derived from two or more monomers where the monomers are on the same arm, and wherein the star polymer is derived from at least two monomers comprising: (a) at least 50 wt% of a C12 to C15 alkyl substituted (meth)acrylate monomer; and (b) less than 50 wt% of an alkyl (meth)acrylate monomer containing 1 to 30 carbon atoms other than the C12 to C15 alkyl (meth)acrylate monomer; and (c) optionally containing less than 20 wt% styrene; and (d) optionally containing less than 10 wt% alkyl methacrylamide; (a) at least 50 wt% of a C12 to C15 alkyl substituted (meth)acrylate monomer; and (b) less than 50 wt% of an alkyl (meth)acrylate monomer containing 1 to 30 carbon atoms other than the C12 to C15 alkyl (meth)acrylate monomer; and (c) optionally containing less than 20 wt% styrene; and (d) optionally containing less than 10 wt% alkyl methacrylamide; optionally contacting the polymer prepared by step or step with a polymerisation inhibitor; and mixing the polymer prepared by step or step with an oil of lubricating viscosity to form a lubricating composition.