Ethylene-propylene branched copolymers as viscosity modifiers

A method of making a lubricant composition, comprising:

• blending an oil with a long chain branched copolymer, the composition having:
• a shear stability index (30 cycles) of from about 2% to about 80%;
• and
• a kinematic viscosity at 100° C. of from about 3 cSt to about 30 cSt, and wherein the copolymer has:
• a Mw(LS)/Mn(DRI) from about 1.5 to about 6;
• a Mw(LS) from about 20,000 to about 600,000 g/mol;
• a g′vis of from about 0.7 to about 0.98;
• and
• an ethylene content of about 20 wt % to about 90 wt %,
• and wherein the copolymer comprises a remnant of a metal hydrocarbenyl chain transfer agent, wherein the metal hydrocarbenyl chain transfer agent is represented by formula:
• wherein each R′, independently, is a C1-C30 hydrocarbyl group;
• each R″, independently, is a C4-C20 hydrocarbenyl group having an end-vinyl group;
• and v is from 0.1 to 3.

A method of lubricating an engine, comprising:

• supplying to the engine a lubricant composition comprising an oil and a long chain branched copolymer having:
• a shear stability index (30 cycles) of from about 2% to about 80%;
• and a kinematic viscosity at 100° C. of from about 3 cSt to about 30 cSt;
• wherein the copolymer has:
• a Mw(LS)/Mn(DRI) from about 1.5 to about 6;
• a Mw(LS) from about 20,000 to about 600,000 g/mol;
• a g′vis of from about 0.7 to about 0.98;
• an ethylene content of about 20 wt % to about 90 wt %;
• and
• wherein the copolymer comprises a remnant of a metal hydrocarbenyl chain transfer agent, wherein the metal hydrocarbenyl chain transfer agent is represented by formula:
• wherein each R′, independently, is a C1-C30 hydrocarbyl group;
• each R″, independently, is a C4-C20 hydrocarbenyl group having an end-vinyl group;
• and v is from 0.1 to 3.