The present invention relates to the use of a lubricating composition comprising: -at least one base oil; and -at least one monoester which is separate from the base oil and formed between a linear, saturated or unsaturated C.sub.8-C.sub.14 monocarboxylic acid, and a branched, saturated or unsaturated C.sub.4-C.sub.16 monoalcohol to reduce the fuel consumption of a vehicle fitted with a transmission member, in particular a gearbox and/or an axle, which is lubricated by means of said composition.

The present invention relates to the use of a lubricating composition comprising: -at least one base oil; and -at least one monoester which is separate from the base oil and formed between a linear, saturated or unsaturated C.sub.8-C.sub.14 monocarboxylic acid, and a branched, saturated or unsaturated C.sub.4-C.sub.16 monoalcohol to reduce the fuel consumption of a vehicle fitted with a transmission member, in particular a gearbox and/or an axle, which is lubricated by means of said composition.

Disclosed is a lubricating oil composition capable of having a good balance of electrical insulation, seizure resistance and wear resistance. In particular, the lubricating oil composition comprises: (A) a lubricant base oil; (B) an alkaline earth metal detergent; (C) a triazole-based compound represented by the following general formula (1) or (2):

##STR00001##

wherein R.sup.1-R.sup.6 are as defined herein; (D) at least one sulfur-containing compound selected from the group consisting of a sulfur-containing heterocyclic ether compound and a sulfide compound; and (E) an ashless dispersant.

Disclosed is a lubricating oil composition capable of having a good balance of electrical insulation, seizure resistance and wear resistance. In particular, the lubricating oil composition comprises: (A) a lubricant base oil; (B) an alkaline earth metal detergent; (C) a triazole-based compound represented by the following general formula (1) or (2):

##STR00001##

wherein R.sup.1-R.sup.6 are as defined herein; (D) at least one sulfur-containing compound selected from the group consisting of a sulfur-containing heterocyclic ether compound and a sulfide compound; and (E) an ashless dispersant.

The present invention relates to a lubricating oil composition containing a base oil (A) containing an olefin-based polymer (A1) having an area ratio of a peak derived from a hydride (A11) of a decene trimer of 80% or more relative to 100% of a total area of peaks derived from the olefin-based polymer (A1) detected in a chromatogram and having predetermined kinematic viscosity, flash point, and pour point, a viscosity index improver (B) containing a comb-shaped polymer (B1), and an organic molybdenum-based compound (C), in which the content of the comb-shaped polymer (B1) is regulated within a specified range and having a HTHS viscosity at each of 150° C. and 50° C. of the lubricating oil composition and a NOACK value in predetermined ranges, respectively.

Disclosed is a method for reducing corrosion in a hybrid engine. The method includes the steps of lubricating a hybrid engine with a lubricating oil composition having a major amount of an oil of lubricating viscosity; a minor amount of a salicylate detergent derived from an isomerized normal alpha olefin; and a minor amount of a dispersant.

Disclosed is a method for reducing corrosion in a hybrid engine. The method includes the steps of lubricating a hybrid engine with a lubricating oil composition having a major amount of an oil of lubricating viscosity; a minor amount of a salicylate detergent derived from an isomerized normal alpha olefin; and a minor amount of a dispersant.

A lubricating oil composition for a transmission, the composition including: (A) a lubricant base oil comprising a mineral base oil and/or a synthetic base oil; and (B) a poly(meth)acrylate having a weight average molecular weight of no more than 25,000, wherein the composition has a kinematic viscosity at 100° C. of 2.5 to 4.9 mm.sup.2/s.

A lubricating oil composition for a transmission, the composition including: (A) a lubricant base oil comprising a mineral base oil and/or a synthetic base oil; and (B) a poly(meth)acrylate having a weight average molecular weight of no more than 25,000, wherein the composition has a kinematic viscosity at 100° C. of 2.5 to 4.9 mm.sup.2/s.

Provided is a mineral base oil satisfying the following requirements (I) to (III): Requirement (I): a kinematic viscosity at 100° C. is 2 mm.sup.2/s or more and less than 7 mm.sup.2/s; Requirement (II): a viscosity index is 100 or more; and Requirement (III): a temperature gradient Δ|η*| of complex viscosity between two temperature points −10° C. and −25° C. is 60 Pa.Math.s/° C. or less as measured with a rotary rheometer under conditions at an angular velocity of 6.3 rad/s and a strain amount of 0.1 to 100%. The foregoing mineral base oil can become a lubricating oil composition having desirable low-temperature viscosity characteristics, including low-temperature fuel consumption and low-temperature engine start-up performance, and also having excellent high-temperature piston detergency.