Fuels, hydraulic fluids and lubricants made of or comprising a portion of renewable hydrocarbon raw materials, as well as biodegradable fuels, hydraulic fluids and lubricants are known to support microbial growth. Highly toxicorganic biocides have been added to reduce microbial growth. The use of such biocides can now be avoided, by instead using a stable solution of boric acid in a solvent, the boric acid being completely dissolved or at least free from any particles larger than 100 nm in size, and adding this solution to the fuel, hydraulic fluid or lubricant to give a final concentration of boron in the range of 1-100 ppm, preferably 1-50 ppm in the product. While preventing microbial growth, the addition of boron also reduces corrosion, in particular microbiologically induced corrosion (MIC).

An object of the present invention is to provide a lubricant base oil for power transmission (in particular, a lubricant base oil for traction drives) having a high traction coefficient and a high flash point. The present invention relates to a lubricant base oil for power transmission comprising an alicyclic dicarboxylic acid diester compound represented by general formula (1): ##STR00001##
wherein R.sup.1 to R.sup.5 are the same or different, and each represents hydrogen or linear or branched C.sub.1-4 alkyl, and two R.sup.1, two R.sup.2, two R.sup.3, two R.sup.4, and two R.sup.5 may respectively be the same or different; and ring A is ##STR00002##
wherein R represents C.sub.1-3 alkyl, and n represents 0, 1, or 2; when n represents 2, R may be the same or different.

A method for the regeneration of used lubricating oils to produce lubricant base oils includes the steps of (a) removing resin and impurities by distillation, (b) catalytic oxidation treatment and (c) adsorption process. The method can efficiently reduce the color, metal ions, and sulfur content under mild reaction conditions at low cost and obtain high yield of regenerated oil above 85 wt. %.

A lubricating oil composition including: at least one base oil selected from a mineral oil-based lubricating oil, a synthetic oil-based lubricating oil, or a mixed oil thereof, and zinc dialkyldithiophosphates X consisting of the compounds Z.sub.1 to Z.sub.3 represented by the formulae (1) to (3) are contained, in which a total content of the zinc dialkyldithiophosphates X is 0.02% by mass or more in terms of phosphorus concentration with respect to the total mass of the oil composition, and the zinc dialkyldithiophosphates X satisfy the formulae (a) to (c). In the formula (1), each of R.sup.1 to R.sup.4 independently represents a linear or branched primary alkyl group having from 10 to 20 carbon atoms. In the formula (2), each of R.sup.5 to R.sup.8 independently represents a linear or branched primary alkyl group having from 7 to 9 carbon atoms. In the formula (3), each of R.sup.9 to R.sup.12 independently represents a linear or branched primary or secondary alkyl group having from 3 to 6 carbon atoms. The formula (a) to (c) are shown in the specification.

Disclosed is a method of producing a lubricating base oil, including providing a feedstock including a diesel fraction, subjecting the feedstock to catalytic dewaxing, and recovering a lubricating base oil from a product of the catalytic dewaxing. A lubricating base oil produced thereby and a lubricant product including the lubricating base oil are also provided.

A method for producing a wax isomerized oil, comprising a step of providing an ethylene polymer wax, a step of hydrocracking the ethylene polymer wax by a hydrocracking catalyst to obtain a cracked product, and a step of isomerization dewaxing the cracked product by a hydroisomerization catalyst to obtain a wax isomerized oil.

A lubricating grease composition includes a base oil, a thickener, and a solid lubricant, wherein the base oil is a synthetic hydrocarbon oil with a kinematic viscosity of 600 to 2000 mm.sup.2/s at 40 C., the thickener is a barium complex soap, and the solid lubricant is an inorganic fine particle with Mohs hardness of 3 to 6 and an average particle size of 10 to 40 m.

The lubricating oil composition of the present invention contains a base oil, a 2,6-di-tert-butylphenol (A), and at least one compound (B) selected from a benzotriazole compound and a sorbitan compound.

A multi-functional olefin copolymer viscosity index improver and a lubricating oil composition including such lubricant additive that provides improved viscometric properties and helps reduce low speed pre-ignition events at the same time. In one approach, the multi-functional olefin copolymer viscosity index improver is silicone functionalized and includes an acylated olefin copolymer with aminosilane or aminosiloxone pendant or side groups.

The invention provides a hydraulic fluid composition comprising a hydrocarbon component comprising more than 5 wt % of naphthenic oil and up to 95 wt % of renewable or recycled isoparaffinic oil, based on the total weight of the composition. The hydraulic fluid composition is useful as an arctic hydraulic fluid composition, shock absorber or automatic transmission fluid.