A lubricating oil composition may include a base oil (A), succinimide (B) which has not been modified with boron, succinimide (C) modified with boron, a metallic detergent (D), and an antioxidant (E), wherein the ratio of the content of boron atoms derived from ingredient (C) to the content of nitrogen atoms derived from ingredients (B) and (C), B/N, is 0.30 or less by mass, the lubricating oil composition satisfying requirement (I) and/or requirement (II). Requirement (I): Ingredient (D) includes a metallic detergent (D1) having a base value less than 100 mgKOH/g. Requirement (II): Ingredient (E) includes an amine-based antioxidant (E1), the content of ingredient (E1) being 1.00 mass % or less.

A lubricating oil composition may include a base oil (A), succinimide (B) which has not been modified with boron, succinimide (C) modified with boron, a metallic detergent (D), and an antioxidant (E), wherein the ratio of the content of boron atoms derived from ingredient (C) to the content of nitrogen atoms derived from ingredients (B) and (C), B/N, is 0.30 or less by mass, the lubricating oil composition satisfying requirement (I) and/or requirement (II). Requirement (I): Ingredient (D) includes a metallic detergent (D1) having a base value less than 100 mgKOH/g. Requirement (II): Ingredient (E) includes an amine-based antioxidant (E1), the content of ingredient (E1) being 1.00 mass % or less.

The present invention relates to a lubricant composition, in particular for a gas or steam turbine, comprising: —at least one base oil; —at least one phenylnaphthylamine (PAN) compound, preferably alkylphenyl-α-naphthylamine (APAN) compound; —at least one diphenylamine (DPA) compound, preferably dialkyl-diphenylamine compound; and —at least one phosphite ester compound, preferably triaryl phosphite ester compound; in which the ratio by weight between said diphenylamine compound(s) and said phosphite ester compound(s) is strictly greater than 1.0.

The present invention relates to a lubricant composition, in particular for a gas or steam turbine, comprising: —at least one base oil; —at least one phenylnaphthylamine (PAN) compound, preferably alkylphenyl-α-naphthylamine (APAN) compound; —at least one diphenylamine (DPA) compound, preferably dialkyl-diphenylamine compound; and —at least one phosphite ester compound, preferably triaryl phosphite ester compound; in which the ratio by weight between said diphenylamine compound(s) and said phosphite ester compound(s) is strictly greater than 1.0.

A lubricating oil composition including a base oil (X) having a tertiary carbon atom at a content of 8.0 at % or more based on the total carbon of hydrocarbons and an antioxidant (Y) having an amine-based antioxidant (A), a phenol-based antioxidant (B), and a phosphor-based antioxidant (C). The amine-based antioxidant (A) includes a diphenylamine compound (A1) represented by the following general formula (a1):

##STR00001##

where R.sup.a1 and R.sup.a2, na1 and na2 are defined in the disclosure.

A lubricating oil composition including a base oil (X) having a tertiary carbon atom at a content of 8.0 at % or more based on the total carbon of hydrocarbons and an antioxidant (Y) having an amine-based antioxidant (A), a phenol-based antioxidant (B), and a phosphor-based antioxidant (C). The amine-based antioxidant (A) includes a diphenylamine compound (A1) represented by the following general formula (a1):

##STR00001##

where R.sup.a1 and R.sup.a2, na1 and na2 are defined in the disclosure.

A lubricant composition comprising an oil-soluble polyalkylene glycol; an ester compound selected from the group of natural esters and synthetic esters, and combinations thereof; and an additive mixture comprising an antioxidant and an anticorrosive, wherein the anticorrosive is selected from neutral alkali metal and alkaline earth metal salts of sulfonic acids, carboxylic acids, naphthoic acids, naphthenic acids, benzoic acids and phosphoric acids, and derivatives and combinations thereof.

A lubricant composition comprising an oil-soluble polyalkylene glycol; an ester compound selected from the group of natural esters and synthetic esters, and combinations thereof; and an additive mixture comprising an antioxidant and an anticorrosive, wherein the anticorrosive is selected from neutral alkali metal and alkaline earth metal salts of sulfonic acids, carboxylic acids, naphthoic acids, naphthenic acids, benzoic acids and phosphoric acids, and derivatives and combinations thereof.

An object of the present invention is to provide an ester-based lubricating base oil for a fluid bearing that has a high viscosity index and excellent evaporation resistance, hydrolytic stability, and low-temperature fluidity. The present invention relates to a lubricating base oil for a fluid bearing containing a compound represented by general formula (1):

##STR00001##

wherein R.sup.1 represents a linear C.sub.2-C.sub.16 alkyl group, m represents an integer of 2 to 10, and n represents an integer of 4 to 14.

An object of the present invention is to provide an ester-based lubricating base oil for a fluid bearing that has a high viscosity index and excellent evaporation resistance, hydrolytic stability, and low-temperature fluidity. The present invention relates to a lubricating base oil for a fluid bearing containing a compound represented by general formula (1):

##STR00001##

wherein R.sup.1 represents a linear C.sub.2-C.sub.16 alkyl group, m represents an integer of 2 to 10, and n represents an integer of 4 to 14.