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 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.

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.

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.

The invention is directed to a zinc-free lubricating composition for an internal combustion engine containing a phosphorus anti-wear agent, an ashless antioxidant, and a metal-free basic detergent. The lubricating composition provides wear protection, deposit control, and improved acid control with reduced levels of metal-containing additives.

The invention is directed to a zinc-free lubricating composition for an internal combustion engine containing a phosphorus anti-wear agent, an ashless antioxidant, and a metal-free basic detergent. The lubricating composition provides wear protection, deposit control, and improved acid control with reduced levels of metal-containing additives.

The present invention relates to a hydraulic fluid composition containing a base oil (A), an antioxidant (B) including an amine-based antioxidant (B1) and a phenol-based antioxidant (B2), and a succinimide-based compound (C), wherein the hydraulic fluid composition satisfies the following requirement (I); and is to be used for hydraulic equipment which is equipped with at least one of a wet type brake and a wet type clutch and which is selected from a construction machinery, a general industrial machinery, and a power generator, and in which a working pressure is 30 MPa or more. The hydraulic fluid composition is not only excellent in wear resistance and an effect for suppressing the sludge formation but also excellent in a braking performance or a clutch performance, even when used under a high-pressure condition. Requirement (I): A static friction coefficient (μ.sub.s) after 1,000 cycles, as measured in conformity with the SAE No. 2 test described in JCMAS P 047:2004, is 0.100 to 0.162.

The present invention relates to a hydraulic fluid composition containing a base oil (A), an antioxidant (B) including an amine-based antioxidant (B1) and a phenol-based antioxidant (B2), and a succinimide-based compound (C), wherein the hydraulic fluid composition satisfies the following requirement (I); and is to be used for hydraulic equipment which is equipped with at least one of a wet type brake and a wet type clutch and which is selected from a construction machinery, a general industrial machinery, and a power generator, and in which a working pressure is 30 MPa or more. The hydraulic fluid composition is not only excellent in wear resistance and an effect for suppressing the sludge formation but also excellent in a braking performance or a clutch performance, even when used under a high-pressure condition. Requirement (I): A static friction coefficient (μ.sub.s) after 1,000 cycles, as measured in conformity with the SAE No. 2 test described in JCMAS P 047:2004, is 0.100 to 0.162.

A grease composition may contain a base oil (A) and a urea-based thickener (B). Particles containing the urea-based thickener (B) in the grease composition may satisfy requirement (I). The base oil (A) may be a mixed base oil containing a high-viscosity base oil (A1) having a kinematic viscosity at 40° C. of 250 mm.sup.2/s to 550 mm.sup.2/s, a low-viscosity base oil (A2) having a kinematic viscosity at 40° C. of 5.0 mm.sup.2/s to 110 mm.sup.2/s, and an ultra-high viscosity hydrocarbon-based synthetic oil (A3) having a number average molecular weight (Mn) of 2,500 to 4,500 and a kinematic viscosity at 40° C. of 25,000 mm.sup.2/s to 50,000 mm.sup.2/s. The base oil (A) may have a kinematic viscosity at 40° C. of 25 mm.sup.2/s to 105 mm.sup.2/s and a viscosity index of 120 or more. Both low-temperature characteristics and a lubricating life can be achieved.

A grease composition may contain a base oil (A) and a urea-based thickener (B). Particles containing the urea-based thickener (B) in the grease composition may satisfy requirement (I). The base oil (A) may be a mixed base oil containing a high-viscosity base oil (A1) having a kinematic viscosity at 40° C. of 250 mm.sup.2/s to 550 mm.sup.2/s, a low-viscosity base oil (A2) having a kinematic viscosity at 40° C. of 5.0 mm.sup.2/s to 110 mm.sup.2/s, and an ultra-high viscosity hydrocarbon-based synthetic oil (A3) having a number average molecular weight (Mn) of 2,500 to 4,500 and a kinematic viscosity at 40° C. of 25,000 mm.sup.2/s to 50,000 mm.sup.2/s. The base oil (A) may have a kinematic viscosity at 40° C. of 25 mm.sup.2/s to 105 mm.sup.2/s and a viscosity index of 120 or more. Both low-temperature characteristics and a lubricating life can be achieved.