A viscosity index improver containing, in non-ester diluent oil, one or more hydrogenated, functionalized linear block copolymers having at least one block derived from monoalkenyl arene covalently linked to at least one block derived from diene in an amount that is greater than the critical overlap concentration (c.sub.h*), in mass %, for the linear block copolymers in the diluent oil; and an amount of ester base stock.

A viscosity index improver containing, in non-ester diluent oil, one or more hydrogenated, functionalized linear block copolymers having at least one block derived from monoalkenyl arene covalently linked to at least one block derived from diene in an amount that is greater than the critical overlap concentration (c.sub.h*), in mass %, for the linear block copolymers in the diluent oil; and an amount of ester base stock.

A viscosity index improver containing, in diluent oil, one or more optionally functionalized linear block copolymers having at least one block derived from alkenyl arene covalently linked to at least one block derived from diene in an amount that is greater than the critical overlap concentration (c.sub.h*), in mass %, for the linear block copolymers in the diluent oil; and ester base stock and/or at least one star (or radial) polymer, the star polymer being present in an amount such that the c/c.sub.h* value of the star polymer in the concentrate falls within the range of from 0.01 to about 1.6, wherein c is the concentration in mass % of star polymer in the concentrate and c.sub.h* is the critical overlap concentration in mass % for the star polymer in the diluent oil used to form the concentrate.

A viscosity index improver containing, in diluent oil, one or more optionally functionalized linear block copolymers having at least one block derived from alkenyl arene covalently linked to at least one block derived from diene in an amount that is greater than the critical overlap concentration (c.sub.h*), in mass %, for the linear block copolymers in the diluent oil; and ester base stock and/or at least one star (or radial) polymer, the star polymer being present in an amount such that the c/c.sub.h* value of the star polymer in the concentrate falls within the range of from 0.01 to about 1.6, wherein c is the concentration in mass % of star polymer in the concentrate and c.sub.h* is the critical overlap concentration in mass % for the star polymer in the diluent oil used to form the concentrate.

A grease composition comprising a lubricating base oil and a thickener, which thickener comprises an ester-terminated oligomer and a polymer. The polymer is a polyolefin. The ester-terminated oligomer has the general formula: R1O[COR2CONHR3NHCOR2CO].sub.nOR1. R1 each independently represent a hydrocarbon group containing 4-22 carbon atoms. R2 represents a hydrocarbon group containing 4-42 carbon atoms. R3 represents a hydrocarbon group containing 2-9 carbon atoms. n represents an integer in the range of 1-20. A method for preparing the present grease composition. The present grease composition can be used for (a) lubricating a mechanical component having a metal surface and (b) protecting a mechanical component having a metal surface against corrosion, wear and/or fretting.

A grease composition comprising a lubricating base oil and a thickener, which thickener comprises an ester-terminated oligomer and a polymer. The polymer is a polyolefin. The ester-terminated oligomer has the general formula: R1O[COR2CONHR3NHCOR2CO].sub.nOR1. R1 each independently represent a hydrocarbon group containing 4-22 carbon atoms. R2 represents a hydrocarbon group containing 4-42 carbon atoms. R3 represents a hydrocarbon group containing 2-9 carbon atoms. n represents an integer in the range of 1-20. A method for preparing the present grease composition. The present grease composition can be used for (a) lubricating a mechanical component having a metal surface and (b) protecting a mechanical component having a metal surface against corrosion, wear and/or fretting.

An electrical discharge machining oil composition of the invention includes an organic acid metal salt and a base oil, in which the organic acid metal salt is an organic acid salt of a metal having an electronegativity on Pauling scale of 2 or less, and the present composition has a volume resistivity at 80 degrees C. of 2?10.sup.?5 T?.Math.m or more and a kinematic viscosity at 40 degrees C. in a range from 0.5 mm.sup.2/s to 10 mm.sup.2/s.

An electrical discharge machining oil composition of the invention includes an organic acid metal salt and a base oil, in which the organic acid metal salt is an organic acid salt of a metal having an electronegativity on Pauling scale of 2 or less, and the present composition has a volume resistivity at 80 degrees C. of 2?10.sup.?5 T?.Math.m or more and a kinematic viscosity at 40 degrees C. in a range from 0.5 mm.sup.2/s to 10 mm.sup.2/s.

A lubricant composition including a polyalphaolefin base oil component in an amount of about 30 wt. % to about 70 wt. % based on total weight of said lubricant composition and a thickener in an amount up to 30 wt. % based on total weight of said lubricant composition. The lubricant composition has a kinematic viscosity at 100 C. of about 5 cSt to about 15 cSt and a kinematic viscosity of at 40 C. about 30 cSt to about 70 cSt, each measured in accordance with ASTM D445.

A lubricant composition including a polyalphaolefin base oil component in an amount of about 30 wt. % to about 70 wt. % based on total weight of said lubricant composition and a thickener in an amount up to 30 wt. % based on total weight of said lubricant composition. The lubricant composition has a kinematic viscosity at 100 C. of about 5 cSt to about 15 cSt and a kinematic viscosity of at 40 C. about 30 cSt to about 70 cSt, each measured in accordance with ASTM D445.