Base stocks having Group III/III+ characteristics are prepared from certain advantageous crude oils via simplified process configurations and/or under less severe process conditions. Crude oils comprising a vacuum gas oil (VGO) fraction having a ratio of a sum of paraffin content plus 1-Ring species content to multi-ring species content that is greater than or equal to about 1.5 are advantageous in this context. Other parameters such as API gravity and crude compositional ranges may also be considered for identifying advantageous crudes. In some instances, advantageous crudes are processed into Group III base stocks via a process configuration in which the crude oil is directly supplied to a hydroprocessing unit.

Provided herein are hydrocarbon mixtures with controlled structure characteristics that address the performance requirements for finished lubricants driven by the stricter environmental and fuel economy regulations. The branching characteristics of the hydrocarbon molecules are controlled to provide a composition that has a unique and superior viscosity-temperature relationship and Noack volatility. An important aspect of the present invention relates to a saturated hydrocarbon mixture with at least 80% of the molecules having an even carbon number, with the branching characteristic of BP/BI in the range 0.6037 (Internal alkyl branching)+2.0, where on average at least 0.3 to 1.5 of the internal methyl branches are located more than 4 carbons away from the terminal carbon when analyzed by carbon NMR. The saturated hydrocarbon mixture with such unique branching structure consistently exhibits a stand out performance in the cold crank simulated viscosity (CCS) vs Noack volatility relationship, which allows for the formulation of lower viscosity engine oils with improved fuel economies.

A lubricant oil composition for automotive gears includes a lubricant base oil including a mineral oil having a kinematic viscosity at 100 C. of 2.0 to 6.5 mm.sup.2/s, a viscosity index of not less than 105 and a pour point of not more than 10 C., and/or a synthetic oil having a kinematic viscosity at 100 C. of 1.0 to 6.5 mm.sup.2/s, a viscosity index of not less than 120 and a pour point of not more than 30 C.; and an ethylene/-olefin copolymer having an ethylene content of 55 to 85 mol %, a kinematic viscosity at 100 C. of 10 to 200 mm.sup.2/s, a molecular weight distribution of not more than 2.2, and a melting point in the range of 30 C. to 60 C. The lubricant oil composition for automotive gears has a kinematic viscosity at 100 C. of 4.0 to 9.0 mm.sup.2/s.

A polymer composition contains a comb-shaped polymer (X) containing the following structural units (a) to (c): (a): a structural unit derived from a short-chain alkyl (meth)acrylate (A) having a short-chain alkyl group having 1 to 5 carbon atoms; (b): a structural unit derived from a long-chain alkyl (meth)acrylate (B) having a long-chain alkyl group having 6 to 32 carbon atoms; and (c): a structural unit derived from a macromonomer (C), a content of the structural unit (a) being 70% by mass or more based on the total structural units of the comb-shaped polymer (X); and a hetero atom-containing base oil (Y). The hetero atom-containing base oil (Y) has a kinematic viscosity at 40? C. of 25 mm.sup.2/s or less.

In a method and a system for purification of contaminated oil, the contaminated oil and a liquid separation aid are provided in a mixing tank and then mixed into a mixture. Thereafter, the mixture is filtered.

Disclosed are solvency enhancer compositions, for example, as additives to lubricating oils and as formulated in lubricating oil compositions and associated methods of preparation and use thereof. The compositions and methods can dissolve at least one of oxidation products and other organic polar compounds, due to lubricant degradation, formed and suspended in oil compositions including adding an effective amount of a solvency enhancer to the oils, wherein the solvency enhancer includes Guerbet alcohols. Further described are methods for dissolving organic deposits in an oil system including adding an effective amount of a solvency enhancer to the oil system, wherein the solvency enhancer includes Guerbet alcohols. Also provided are methods for preventing sludge and varnish formation in in-service oils including adding an effective amount of a solvency enhancer to the oils, wherein the solvency enhancer includes Guerbet alcohols.

One aspect of the present invention relates to a dinaphthyl ether compound represented by formula (1):

##STR00001##

in the formula (1), R.sup.1 and R.sup.2 are the same or different and each represent a linear or branched hydrocarbon group having 6 to 32 carbon atoms; m and n are each a real number of 0 or more and satisfy 1.0?m+n?3.0.

One aspect of the present invention relates to a naphthyl phenyl ether compound represented by formula (1):

##STR00001##

in the formula (1), R.sup.1 and R.sup.2 are the same or different and each represent a linear or branched hydrocarbon group having 6 to 28 carbon atoms; m and n are each a real number of 0 or more and satisfy 1.0?m+n?3.0.

There is disclosed an antifoam component for a mechanical device which includes a fluorinated poly(acrylate) copolymer. The antifoam component has improved foam performance and thermal stability in finished fluids, such as driveline fluids.

An object of the present invention is to provide a lubricating oil composition for hydraulic actuation which has excellent safety and which is imparted with electrical conductivity in order to prevent the generation of noise that adversely affects devices including hydraulic circuits equipped with an electronic control device for the valve system. The composition uses a hydrocarbon base oil, and the base oil contains from 30 to 250 ppm of ultrabasic magnesium salicylate in terms of magnesium content relative to the total amount of the composition, and from 0.07 to 5.0 mass % of non-dispersible polymethacrylate having a weight-average molecular weight of from 5,000 to 200,000 as a net amount relative to the total amount of the composition. The conductivity of the composition at 25 C. is 200 pS/m or more, the flash point is 240 C. or more, the pour point is negative 40 C. or less, and the coefficient of friction at 140 C. by a microclutch is 0.08 or more. This lubricating oil composition can be imparted with conductivity in order to prevent the generation of noise that adversely affects electronic controls when used in machinery equipped with electronic control devices.