Provided is a lubricating grease used for lubricating mechanical elements having a reciprocating sliding ball interposed therebetween and maintaining flaking resistance even under a high load in mechanical elements having a reciprocating sliding ball interposed therebetween. The present invention therefore provides a grease composition comprising a base oil (a), a diurea compound (b), an amide compound (c), and a thiophosphorous compound or a thiophosphoric acid ester compound (d), wherein the diurea compound (b) includes a compound represented by Formula (1) R.sub.1—NHCONH—R.sub.2—NHCONH—R.sub.3 (1) wherein R.sub.1 and R.sub.3 represent an acyclic aliphatic hydrocarbon group having from 8 to 20 carbon atoms, and R.sub.2 represents a diphenylmethane group.

Provided is a lubricating grease used for lubricating mechanical elements having a reciprocating sliding ball interposed therebetween and maintaining flaking resistance even under a high load in mechanical elements having a reciprocating sliding ball interposed therebetween. The present invention therefore provides a grease composition comprising a base oil (a), a diurea compound (b), an amide compound (c), and a thiophosphorous compound or a thiophosphoric acid ester compound (d), wherein the diurea compound (b) includes a compound represented by Formula (1) R.sub.1—NHCONH—R.sub.2—NHCONH—R.sub.3 (1) wherein R.sub.1 and R.sub.3 represent an acyclic aliphatic hydrocarbon group having from 8 to 20 carbon atoms, and R.sub.2 represents a diphenylmethane group.

The invention relates to lubricating greases based on alkali metal soaps and/or earth-alkali metal soaps and metal complex soaps based on (R)-10-hydroxyoctadecanoic acid and to the use thereof.

The invention relates to lubricating greases based on alkali metal soaps and/or earth-alkali metal soaps and metal complex soaps based on (R)-10-hydroxyoctadecanoic acid and to the use thereof.

A refrigeration machine oil composition may have good lubricating properties and sufficiently reduce friction even when a base oil containing a low-viscosity mineral oil is used and/or prevent seizure between sliding members. Such refrigeration machine oil compositions may contain a base oil containing a mineral oil, (A) at least one type selected from a specific neutral phosphate ester and an amine salt thereof, and (B) at least one type selected from a specific acidic phosphate ester, an acidic phosphite ester, and an amine salt thereof, and having a kinematic viscosity at 40° C. in a range of from 1.0 to 6.0 mm.sup.2/s.

A lubricating oil composition excellent in the wear resistance and a refrigerator oil composition excellent in the oxidation stability using the lubricating oil composition are provided by a lubricating oil composition containing a base oil (A) and a phosphine derivative (B) having one or more oxygen atom in a molecule.

A lubricating oil composition excellent in the wear resistance and a refrigerator oil composition excellent in the oxidation stability using the lubricating oil composition are provided by a lubricating oil composition containing a base oil (A) and a phosphine derivative (B) having one or more oxygen atom in a molecule.

Disclosed is an additive for lubricating oil, which comprises a phosphite ester compound (A) having a specific structure and a phosphite ester compound (B) having a specific structure, wherein a mass ratio of the phosphite ester compound (A) to the phosphite ester compound (B) (phosphite ester compound (A):phosphite ester compound (B)) is 99:1 to 80:20. According to the present invention, it is possible to provide an additive for lubricating oil, capable of imparting wear resistance and demulsibility with respect to a base oil for lubricating oil, and to impart durability even in the presence of water.

A lubricating oil composition containing a phosphite ester derivative (A) having at least one alkyl group having 1 to 20 carbon atoms in which one —CH.sub.2— group is substituted with a —S— group, and a thiadiazole derivative (B). A method of lubricating an electric drive unit with the lubricating oil composition and an electric drive unit including the lubricating oil composition.

A lubricating oil composition containing a phosphite ester derivative (A) having at least one alkyl group having 1 to 20 carbon atoms in which one —CH.sub.2— group is substituted with a —S— group, and a thiadiazole derivative (B). A method of lubricating an electric drive unit with the lubricating oil composition and an electric drive unit including the lubricating oil composition.