Provided is a lubricating oil composition for use in turbomachinery, compressors, hydraulic equipments, or machine tools, which contains a mineral oil (A) and a synthetic oil (B) containing a polyalkylene glycol (B1) and a polyol ester (B2), in which the content of the mineral oil (A) is 5 to 95% by mass based on the total amount of the lubricating oil composition, and which is used in turbomachinery, compressors, hydraulic equipments, or machine tools. The lubricating oil composition is excellent in oxidation stability, has a strong effect of preventing sludge precipitation and has excellent water separability even in use for a long period of time in high-temperature environments.

A method having the step of using a compound as an additive for: gear oil, grease, engine oil, combustion-engine lubricant, automatic transmission fluid, two-cycle engine lubricant, marine-engine lubricant, or anti-wear agent, the compound having the structure: ##STR00001##
wherein each R is an independently selected alkylphenol-free moiety that is a C.sub.1-22 alkyl, C.sub.6-40 cycloalkyl, C.sub.3-20 methoxy alkyl glycol ether, C.sub.3-20 alkyl glycol ether, or Y—OH moiety; wherein each Y is an independently selected alkylphenol-free moiety that is a C.sub.2-40 alkylene, C.sub.6-40 cycloalkylene, C.sub.2-20 alkylene glycol ether, or C.sub.3-40 alkylene lactone moiety; wherein each m is an independently selected integer ranging from 1 to 100; and wherein x is an integer ranging from 1 to 1000.

Ethylene-C.sub.3-C.sub.10 alpha olefin copolymers, dispersants and lubricating oils/fuel compositions incorporating dispersants, and related methods are generally described herein. The copolymer may comprise ethylene-derived units and C.sub.3-C.sub.10 alpha-olefin-derived units. The C.sub.3-C.sub.10 alpha-olefin-derived units may have a carbon number from three to ten. For example, the C.sub.3-C.sub.10 alpha-olefin-derived units may be propylene-derived units. The dispersants may be made from copolymers having low metal and/or fluorine contents.

A composition obtained by reacting an O,O-dialkyldithiophosphoric acid with a hydroxyalkyl acrylate or a hydroxyalkyl methacrylate, and reacting the product thereof with a dialkylphosphite provides good antiwear protection.

One aspect of the present invention is a refrigerating machine oil containing: a base oil containing an ester of an alcohol and a fatty acid; a compound represented by the following formula (1):

##STR00001##

wherein R.sup.1 and R.sup.2 each independently represent a monovalent hydrocarbon group, R.sup.3 represents a divalent hydrocarbon group, and R.sup.4 represents hydrogen atom or a monovalent hydrocarbon group, and the refrigerating machine oil having a kinematic viscosity at 40 C. of 10 mm.sup.2/s or less.

A refrigerating machine oil having a kinematic viscosity at 100 C. of 0.5 mm.sup.2/s or more and 2.5 mm.sup.2/s or less, a distillation end point in gas chromatography distillation of 380 C. or more and 450 C. or less, and a sulfur content of 0.001 mass % or more and 0.2 mass % or less.

A refrigerating machine oil containing: a lubricating base oil; and a compound represented by the following formula (1):

##STR00001## wherein R.sup.1 and R.sup.2 each independently represent a monovalent hydrocarbon group, R.sup.3 represents a divalent hydrocarbon group, and R.sup.4 represents hydrogen atom or a monovalent hydrocarbon group, and the refrigerating machine oil having a kinematic viscosity at 100 C. of 0.5 mm.sup.2/s or more and 2.5 mm.sup.2/s or less.

A composition obtained by reacting an O,O-dialkyldithiophosphoric acid with a hydroxyalkyl acrylate or a hydroxyalkyl methacrylate, and reacting the product thereof with a dialkylphosphite provides good antiwear protection.

The present invention relates to a benzotriazole derivative, a preparation process thereof and the use thereof in preparation of the lubricating oil composition. The structure of the benzotriazole derivative of the present invention is shown by general formula (I). The benzotriazole derivative of the present invention, as the anti-wear additive for lubricating oil, not only has an excellent extreme pressure anti-wear property, but also has one or more excellent properties of thermal oxidation stability, corrosion resistance, rust resistance and anti-friction performance. ##STR00001## In the general formula (I), each of the group(s) and the number(s) are defined as in the description.

Provided are a lubricating oil composition containing a base oil, a specific thiophosphate compound (A) and a molybdenum-based compound (B), which exhibits excellent wear resistance and has a low friction coefficient in a broad range of contact pressures ranging from high to low; and a precision reduction gear using the lubricating oil composition.