A novel hydraulic fluid composition for application to drilling equipment is described herein. These hydraulic fluid compositions permit effective monitoring or controlling well-head pressure of a well during drilling on land or offshore. The hydraulic fluid compositions prevent uncontrolled flow of gas, oil, or another well fluid out of an underground formation during a drilling or extraction process when applied to the drilling equipment. Accordingly, provided is a hydraulic fluid concentrate which contains a water-soluble phosphate ester and a sulfide compound containing at least one SS linkage, at least 10 carbon atoms and at least one terminal carboxylate group, wherein the SS linkage bridges two alkyl groups. Additional components can be added to the concentrate and include one or more alkaline compound, one or more dicarboxylic acid or salt thereof, a water-soluble corrosion inhibitor, a water-soluble biocide, a pour point depressant, and water, ethylene glycol, or a combination thereof. The concentrate is then further diluted by the customer for use as described herein. Particularly, these compositions are effective in reducing seawater corrosion of a metal in contact with the hydraulic fluid composition, reducing bioaccumulation in oil drilling equipment contacted with the hydraulic fluid composition, and have low toxicity to sea life.

The present invention provides a lubricating oil additive, including: a molybdenum compound (A) represented by the following general formula (1); and a sulfur-based composition (B) containing a sulfur-based compound (b-1) represented by the following general formula (2) and at least one kind of sulfur-based compound (b-2) represented by the following general formula (3) or (4), and a lubricating oil composition containing the additive. In the formula (1), R.sup.1 to R.sup.4 each represent alkyl groups having 6 to 18 carbon atoms, the groups being identical to or different from each other, and X.sup.1 to X.sup.4 each independently represent an oxygen atom or a sulfur atom. In the formula (2), R.sup.5 and R.sup.6 each represent alkyl groups having 3 to 24 carbon atoms, the groups being identical to or different from each other, and a and b each represent a number from 1 to 5. In the formulae (3) and (4), R.sup.7 to R.sup.10 each represent alkylene groups having 1 to 28 carbon atoms, the groups being identical to or different from each other, R.sup.11 and R.sup.12 each independently represent a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and c and d each independently represent a number from 1 to 8, provided that at least one of R.sup.11 or R.sup.12 represents an alkyl group having 1 to 3 carbon atoms. ##STR00001##

Provided is a grease composition for a magnet clutch of an automobile, including: a base oil; and a thickener, wherein the composition contains 5% by mass or more of a sulfur content in terms of sulfur element relative to a total mass of the composition.

In the field of lubricating compositions, in particular to the Fuel Economy (FE) properties of lubricating compositions, there is disclosed the combined use of at least one derivative of molybdenum and at least one derivative of boron to maintain the Fuel Economy (FE) properties of a lubricating composition also including at least one base oil. Also disclosed is a use, within a lubricating composition including at least one base oil, of a combination of at least one derivative of molybdenum and at least one derivative of boron, and at least 30 ppm and at most 600 ppm of born boron relative to the weight of the lubricating composition to preserve the Fuel Economy (FE) properties of this lubricating composition.

A water-soluble metalworking fluid of the invention contains a component (A) that is a dicarboxylic acid including a sulfide structure and a component (B) that is a monocarboxylic acid, in which the fluid contains no polyalkylene glycol. A metalworking coolant of the invention is provided by diluting the above-described water-soluble metalworking fluid with water.

The present invention relates to novel sulphur-bridged compounds, in which within the molecule there is at least one fatty acid bonded by way of at least one sulphur bridge to at least one polyalkylene glycol ester, the reaction product of a fatty acid with a polyalkylene glycol, and these have from 8 to 29% by weight sulphur content, to use of these as sulphur carrier and lubricant additive and to production of the said compounds.

Provided are a lubricating oil composition for internal combustion engine capable of preventing a deterioration of the combustion state of a spark-ignition internal combustion engine, specifically, a lubricating oil composition to be used for a spark-ignition internal combustion engine in which a total tension per piston of tensions applied to the piston ring is 100 N or less, the lubricating oil composition being a lubricating oil composition including a base oil, (A) a calcium-based detergent, at least one selected from (B1) a sodium-based additive and (B2) a magnesium-based additive, and (C) an ash-free sulfur-based additive in predetermined contents; a method for producing the lubricating oil composition; a spark-ignition internal combustion engine using the lubricating oil composition; and a method for lubricating the internal combustion engine.

A water-soluble metalworking fluid of the invention contains: a component (A) that is a dicarboxylic acid including a sulfide structure; a component (B) that is a polyalkylene glycol; a component (C) that is polyhydric alcohol polyalkylene oxide adducts; and a component (D) that is a monocarboxylic acid.