A lubricating oil composition, including: a base oil including an ester base oil and a hindered amine compound, where a content of the hindered amine compound is from 0.60 mass % to 10.0 mass % based on a total amount of the lubricating oil composition. An internal combustion engine installed in a hybrid system, the internal combustion engine filled with the lubricating oil composition. A method of lubricating an internal combustion engine installed a hybrid system, including: applying the lubricating oil composition to the internal combustion engine.

Disclosed is an oil composition with improved fuel economy and durability. The oil composition may be effective in improving fuel economy by reduction of friction on sliding parts of vehicle engines and in preventing abrasion of the engines by effective dispersion of soot in respective parts of the engines. The oil composition comprises a detergent dispersant, a friction reducer and a viscosity controller, which are suitably optimized at a mix ratio of those components.

A lubricating oil composition that hardly generates precipitation attributable to a molybdenum compound under the low temperature environment and is excellent in a friction-reducing effect under the low temperature environment is provided.

The lubricating oil composition is one including (A) a lubricating base oil, (B) a molybdenum-based compound, (C) a metal-based detergent, and (D) an ester compound having one or more hydroxyl groups in a molecule thereof, wherein the metal-based detergent (C) includes (C1) a calcium detergent and (C2) a magnesium detergent, and a content of the ester compound (D) having one or more hydroxyl groups in a molecule thereof is 0.03 to 1.20 mass % on a basis of the total amount of the lubricating oil composition.

Provided are a lubricating oil composition for internal combustion engine, containing a lubricating base oil containing a mineral oil and/or a synthetic oil, (A) an overbased calcium salicylate, (B) an overbased magnesium detergent, (C) a binuclear and/or trinuclear organic molybdenum compound, (D) a phenol-based antioxidant, and (E) an amine-based antioxidant, wherein the component (C), the component (D), and the component (E) are contained in specified contents on the basis of the whole amount of the lubricating oil composition; a method for producing the lubricating oil composition for internal combustion engine; and a lubrication method including using the lubricating oil composition for internal combustion engine.

A lubricating oil composition which exhibits an excellent friction-reducing effect and excellent fuel consumption reducing properties is provided.

The lubricating oil composition includes a lubricating base oil (A), a molybdenum compound (B), and an ashless friction modifier (C), wherein the lubricating oil composition includes a binuclear organic molybdenum compound represented by the following general formula (I) as the molybdenum compound (B), with the content of the binuclear organic molybdenum compound as converted into molybdenum atoms being 0.030 mass % or more and 0.140 mass % or less based on the total amount of the lubricating oil composition; and an ester-based ashless friction modifier (C1) and/or an amine-based ashless friction modifier (C2) as the ashless friction modifier (C), with the total content of the ester-based ashless friction modifier (C1) and the amine-based ashless friction modifier (C2) being more than 0.1 mass % and 1.8 mass % or less based on the total amount of the lubricating oil composition:

##STR00001## in the general formula (I), R.sup.1 to R.sup.4 each represents a hydrocarbon group having 4 to 22 carbon atoms, R.sup.1 to R.sup.4 may be the same as or different from each other, and X.sup.1 to X.sup.4 each represents a sulfur atom or an oxygen atom.

The present invention provides a lubricating oil composition comprising: (a) a major amount of a lubricating oil, (a) a diarylamine antioxidant, and (b) an amidine compound of Formula (I),

##STR00001## wherein R.sub.1 is hydrogen, an alkyl or an aromatic group containing 1-30 carbon atoms; x is from 1 to 5; Y is an optional linking alkyl group; Z is carbon or nitrogen; and R.sub.2 is hydrogen or alkyl groups containing 1-30 carbon atoms.

Also provided is a method for lubricating an engine comprising lubricating the engine with said lubricating oil composition.

The lubricating oil composition of the invention comprises a lubricating base oil with a 100 C. kinematic viscosity of 1-20 mm.sup.2/s, (A) a friction modifier, (B) a first overbased metal salt obtained by overbasing an oil-soluble metal salt with an alkaline earth metal borate, and (C) an overbased second oil-soluble metal salt obtained by overbasing an oil-soluble metal salt with an alkaline earth metal carbonate.

A lubricating oil composition of the present invention for an internal combustion engine is prepared by blending (A) a perbasic calcium sulfonate and/or a perbasic calcium phenate having a TBN of 200 mgKOH/g or higher, (B) predetermined binuclear and/or trinuclear organic molybdenum compounds, and (C) a polyalkyl (meth)acrylate having an SSI of 30 or lower into a lubricating base oil composed of a mineral oil and/or a synthetic oil, in which the total content of molybdenum derived from the binuclear and trinuclear organic molybdenum compounds is 0.025% by mass or higher based on the total amount of the composition, and in which the lubricating oil composition has a high-temperature high-shear viscosity at 100 C. of 4.0 to 5.0 mPa.Math.s, a high-temperature high-shear viscosity at 150 C. of 2.5 mPa.Math.s or lower and a NOACK value (250 C., 1 hr) of 15% by mass or less.

A lubricating oil composition which contains, or is made by admixing: (A) an oil of lubricating viscosity, in a major amount; (B) at least one oil-soluble or oil-dispersible sulfurized fatty acid ester, as an additive in an amount providing the lubricating oil composition with greater than or equal to 0.02 mass % sulphur; and, (C) at least one oil-soluble or oil-dispersible alkali metal or alkaline earth metal salicylate detergent, as an additive in an effective minor amount, providing greater than or equal to 5 mmol of salicylate soap per kilogram of the lubricating oil composition,
wherein the lubricating oil composition does not contain a phosphorus ester additive.

Disclosed is a lubricating oil composition comprising the reaction product of a nitrogen containing reactant wherein the nitrogen containing reactant comprises an alkyl di-alkanolamide, an alkyl di-alkanolamine, or mixtures thereof; an acidic molybdenum compound; and a salicylate compound.

Also disclosed is a method for operating an internal combustion engine comprising said lubricating composition and a method for preparing a molybdenum containing friction modifier.