A comb polymer can be used for reducing a Noack evaporation loss of a lubricant composition, especially of an engine oil composition. Application of the comb polymer to the lubricant composition can bring about the desired reduction. The comb polymer can include specified amounts of macromonomer and alkyl acrylates. Resulting lubricant compositions can include the comb polymer.

The present disclosure relates to a single-phase process for the preparation of a calcium sulphonate complex grease. More particularly, a single-phase process for the preparation of a calcium sulphonate complex grease in the absence of boric acid and including the implementation of at least one step under pressure.

The lubricating oil composition of the present invention contains, together with a base oil, a viscosity index improver (A) including a comb-shaped polymer (A1), a detergent dispersant (B) including an alkali metal borate (B1) and an organometallic compound (B2) containing a metal atom selected from an alkali metal atom and an alkaline earth metal atom, and a friction modifier (C) including a molybdenum-containing friction modifier, with the total content of an alkali metal atom and an alkaline earth metal atom being 2,000 mass ppm or less. The lubricating oil composition of the present invention has excellent detergency, fuel saving properties, and LSPI-preventing properties.

A lubricating oil composition which achieves extended anti-shudder durability without causing a decrease in the metal-to-metal friction coefficient, even when the viscosity of the composition is reduced. The lubricating oil composition includes (A) a lubricant base oil, (C) (C-1) a succinimide compound or boronated succinimide compound having a weight-average molecular weight of 4,000 to 7,000, (C-2) a succinimide compound or boronated succinimide compound having a weight-average molecular weight of more than 7,000 to 10,000, and (D) a phosphorus-based extreme pressure agent, the lubricating oil composition does not include zinc dithiophosphate and may optionally include a sulfur-based extreme pressure agent, provided that the content of sulfur-based extreme pressure agent is no more than 0.1 percent by weight of the lubricating oil composition.

A viscosity index improver containing a copolymer (A) whose essential constituent monomer is a monomer (a) having a number average molecular weight of 800 to 4,000 represented by the following formula (1), the copolymer (A) having a solubility parameter in the range of 9.00 to 9.40:

##STR00001##

wherein R.sup.1 is a hydrogen atom or a methyl group; X.sup.1 is a group represented by O, O(AO).sub.m, or NH, AO is a C2-C4 alkyleneoxy group, m is an integer of 1 to 10, each AO may be the same or different when m is 2 or more, and the (AO).sub.m moieties may be randomly bonded or block-bonded; R.sup.2 is a residue after removal of one hydrogen atom from a hydrocarbon polymer whose essential constituent monomer is butadiene in which the butadiene is present in a proportion of 50% by weight or more based on the weight of R.sup.2, or after removal of one hydrogen atom from a polymer formed by partial hydrogenation of the hydrocarbon polymer; and p represents a number of 0 or 1.

Ester compounds, such as for use in a lubricant, are based on di-, tri- or higher functional carboxylic acids according to formula (I)

##STR00001##

A lubricating oil composition contains: a base oil with a kinematic viscosity at 40 degrees C. in a range from 1 mm.sup.2/s to 200 mm.sup.2/s, a viscosity index of 80 or more and a sulfur content of less than 0.03 mass %; a component (A) being a polyacrylate compound with a mass average molecular weight in a range from 10,000 to 100,000; and a component (B) being at least one of phosphorus compounds represented by a formula (1) below. A content of the component (B) is in a range from 0.05 mass % to 2.0 mass % of a total amount of the composition, and a viscosity index of the composition is 160 or more. ##STR00001##

A lubricant composition for engines has at least one base oil and one fatty amine.

The present invention relates to a lubricating composition comprising: at least one base oil; at least one olefin copolymer; at least one detergent; and at least one linear hydrogenated styrene/butadiene copolymer. The invention also relates to the use of said composition for reducing fuel consumption in an engine and for enhancing the cleanliness of a 4-stroke or 2-stroke, preferably 4-stroke, marine engine or of a stationary engine.

Provided is a lubricating oil composition containing a base oil (A) and a viscosity index improver (B) and satisfying the following requirements (I) and (II):

Requirement (I): a kinematic viscosity at 80 C., V.sub.80 of the lubricating oil composition is 11.5 mm.sup.2/s or less;

Requirement (II): a ratio [V.sub.80/T.sub.80] of a kinematic viscosity at 80 C., V.sub.80 (m.sup.2/s) to an oil film thickness measured at a sliding speed of 2.0 m/s, a maximum Hertz pressure of 0.8 GPa, and an oil temperature of 80 C., T.sub.80 (nm) of the lubricating oil composition is less than 0.105 ((m.sup.2/s)/nm).

The lubricating oil composition is excellent in fuel saving properties and anti-wear properties even when it is used in a temperature environment of around 80 C. which is assumed to fall within a range where an engine is practically used.