Lubricating oil compositions are provided herein that comprise a mixture of: (A) a hydrocarbon as a low-viscosity constituent, (B) a polyalkylene glycol (PAG) as a high-viscosity constituent wherein the oxygen/carbon weight ratio is in the range of from 0.450 to 0.580, and (C) a compound as a control constituent wherein the oxygen/carbon weight ratio is in the range of from 0.080 to 0.350. Methods of lubricating a surface using such lubricating compositions are also provided herein.

Lubricating composition for use in the crankcase of an engine comprising: (i) a base oil comprising at least one monoester or a mixture of monoesters, wherein said monoester or mixture of monoesters has a kinematic viscosity at 100 C. of not more than 4 mm.sup.2/s, a viscosity index of at least 130 and a Noack evaporation loss of not more than 20 wt %; and (ii) a polymeric viscosity index improvers selected from (a) one or more comb polymers; (b) a poly(meth)acrylate polymer having 1 to 70 mol % of one or more (meth)acrylate structural units represented by formula (1) below (1) wherein R.sup.1 is a hydrogen atom or a methyl group, and R.sup.2 is a straight chain or branched hydrocarbon group having not less than 16 carbon atoms; (c) styrene-diene hydrogenated copolymers; and (d) mixtures thereof. The lubricating composition of the present invention provides improved fuel economy properties.

Object

To provide a fluid dynamic pressure bearing oil and a fluid dynamic pressure bearing filled with the fluid dynamic pressure bearing oil, and to provide a spindle motor and a disk drive device including the spindle motor in which the fluid dynamic pressure bearing oil and the bearing are used, thereby suppressing adhesion of a volatile component to a magnetic disk or the like even when the fluid dynamic pressure bearing oil is volatilized, so that occurrence of HDD read/write errors can be suppressed.

Solution

A fluid dynamic pressure bearing oil contains at least one compound selected from the group consisting of a monoester compound represented by the following Formula (1) and a diester compound represented by the following Formula (2): R.sub.1C(O)OR.sub.2 (1) (where R.sub.1 is an alkyl group having 10 or more carbon atoms in total, R.sub.2 is an alkyl group having 9 or more carbon atoms in total, and R.sub.3-E.sub.1-R.sub.4-E.sub.2-R.sub.5 (2) (where R.sub.3 and R.sub.5 are each independently an alkyl group having 8 or more carbon atoms in total, R.sub.4 is an alkylene group having 4 or more carbon atoms in total, and E.sub.1 and E.sub.2 are each independently C(O)O or OC(O).

A lubricating oil composition containing a poly--olefin and an antioxidant, in which an evaporation loss by the Noack method is 4.9% by mass or less, a kinematic viscosity at 100 C. is 6.5 mm.sup.2/sec or less, and an amount of the antioxidant with respect to the poly--olefin is 0.05% by mass or more.

An agent for forming a solid lubricating coating film on a tightening surface of a thread portion, in which a solid lubricant is dispersed in a binder resin as a matrix component, a main component of the solid lubricant is melamine cyanurate, and an average particle diameter of the melamine cyanurate is 0.1 m or more and 10.0 m or less, the binder resin contains an alkyd resin and nitrocellulose, and the alkyd resin and nitrocellulose are contained in an amount of 85 wt % or more of the total binder resin component weight, and a total weight of the solid lubricant is 10 parts by weight or more and 100 parts by weight or less based on 100 parts by weight of a total weight of the binder resin.

This invention relates to a lubricating oil composition comprising or resulting from the admixing of: a) 50 to 99 mass % of one or more base oils; b) 0.1 to 15 mass % of one or more functionalized olefin copolymer having an Mn of from 10,000 to 35,000 g/mol; c) 0.1 to 20 mass % of one or more detergents wherein the detergent comprises at least one calcium detergent having a TBN of more than 100 mg KOH/g; at least one calcium detergent having a TBN of 100 mg KOH/g or less; and at least one magnesium detergent, where the difference in the TBN's for the Ca detergents is at least 100 mg KOH/g; d) 0.01 to 40 mass % of one or more dispersants wherein the dispersants comprise at least one borated dispersant and at least one non borated dispersant; e) 0.01 to 20 of mass % sulfurized fatty acid ester; f) 0.01 to 5 mass % of one or more amine or phenol based antioxidants; and g) 0.001 to 15 mass % of molybdenum containing compound, where the lubricating oil composition has: 1) a sulfated ash content of 0.9 mass % or less; 2) a Mack T-11 final soot %@15 cSt of 6.7% or more; 3) a total base number of 5 to 30 mg KOH/g; 4) HTCBT of copper level increase of 20 ppm or less; 5) T-13 IR peak EOT of 40 abs/cm or less; and 6) Cam wear outlet of 45 m or less.

A grease composition includes a base oil, a thickener, and an extreme pressure additive. The base oil contains trimellitate ester and poly--olefin. A proportion of the trimellitate ester to a total amount of the trimellitate ester and the poly--olefin is 10.0 mass % or more and 60.0 mass % or less. The thickener contains lithium 12-hydroxystearate and lithium stearate. A proportion of the lithium 12-hydroxystearate to a total amount of the lithium 12-hydroxystearate and the lithium stearate is 5.0 mass % or more and 95.0 mass % or less. The extreme pressure additive contains molybdenum dialkyl dithiocarbamate. A proportion of the molybdenum dialkyl dithiocarbamate to a total amount of the trimellitate ester, the poly-a-olefin, the lithium 12-hydroxystearate, the lithium stearate, and the molybdenum dialkyl dithiocarbamate is 0.6 mass % or more and 16.0 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.