Provided is a grease composition which contains (A) a mixed base oil containing (A1) a low-viscosity base oil having a kinematic viscosity at 40° C. of 10 to 50 mm.sup.2/s and (A2) a high-viscosity base oil having a kinematic viscosity at 40° C. of 200 to 700 mm.sup.2/s, (B) a lithium-based thickener and (C) a polymer having a kinematic viscosity at 100° C. of 1,000 to 100,000 mm.sup.2/s, and has an apparent viscosity at −10° C., as measured according to JIS K2220:2013 and at a shear rate of 10 s.sup.−1, of 50 to 250 mPa.Math.s. The grease composition is excellent in pumpability and is also excellent in wear resistance under poor lubrication conditions.

A lubricant additive composition and lubricant composition are provided that include one or more friction modifier compounds and antiwear compounds. Methods of lubricating moving metal surfaces of a machine are also provided.

The present disclosure describes lubricant compositions effective to minimize average engine sludge through selection of lubricant additives that control the total nitrogen as well as the origin of the nitrogen in the lubricant composition. In aspects, the lubricant compositions herein include at least a base oil of lubricating viscosity, a dispersant system, and at least one antioxidant.

The present invention provides a hydraulic fluid comprising: (a) 40 to 2000 ppm by weight in terms of nitrogen content of a corrosion inhibiting agent which is one or more compounds of formula (I):

##STR00001## and/or tribologically acceptable salts thereof, wherein in formula (I): each R.sup.1 is independently a hydrocarbyl group comprising 1 to 10 carbon atoms, x is 0 to 4, each of R.sup.2 and R.sup.3 is independently hydrogen or a hydrocarbyl group comprising 1 to 20 carbon atoms, R.sup.4 is —NR.sup.5R.sup.6 or —OR.sup.7, each of R.sup.5 and R.sup.6 is independently an aryl group comprising 6 to 14 carbon atoms, optionally substituted with one or more hydrocarbyl groups comprising 1 to 20 carbon atoms, R.sup.7 is a hydrocarbyl group comprising 1 to 20 carbon atoms, and in each of said hydrocarbyl groups containing 2 or more carbon atoms, the carbon chain may, independently, optionally be interrupted by one or more ether groups; (b) 0.1 to 1% by weight of an ashless dispersant; and (c) a major amount of a base oil.

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.

The present invention relates to a lubricating oil composition containing: (A) a poly-α-olefin base oil obtained by using a metallocene catalyst; (B) a mineral oil-based base oil exhibiting a distillation curve with a temperature gradient Δ|Dt| of distillation temperature between two points 2.0 vol % and 5.0 vol % of distillation amount being 6.8° C./vol % or less; and (C) an ester-based base oil in an amount of 6% by mass or more based on a total amount of the 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.

An aspect of the present invention provides a refrigerating machine oil containing: a lubricating base oil; a phosphorus-containing additive; and a polymer comprising an unsaturated carboxylic acid ester as a monomer unit.

The present invention provides a water/glycol-based hydraulic fluid that includes a total fatty acid and dimer acid of more than 0.4 and no more than 1.2 mass % as a fatty acid lubricant, and also a phosphate ester at between 0.01 and 0.07 mass %. The phosphate ester has the following structure (1) here R1 and R2 each represent a hydrogen atom or a hydrogen group with a carbon number between 1 and 30, and may either be mutually identical or mutually different; R.sub.3 represents a hydrocarbon group with a carbon number between 1 and 20; R.sub.4 represents a hydrogen atom or a hydrocarbon group with a carbon number between 1 and 30; and X.sub.1, X.sub.2, X.sub.3, and X.sub.4 each indicate an oxygen atom or a sulfur atom, where these may either be mutually identical or mutually different.

##STR00001##

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.