The present invention relates to a dinuclear molybdenum complex with ligands selected from fatty tertiary amines of formula (I):

R—N[(CH.sub.2).sub.nR.sup.2][(CH.sub.2).sub.nR.sup.3]  (I)

wherein R represents a linear or branched alkyl comprising 3 to 30 carbon atoms, preferably 3 to 20, advantageously 7 to 17 carbon atoms; n, identical or different, represents 2 or 3; R.sup.2 and R.sup.3, identical or different, represent an O, OR, NR′.sub.2, COOR′, or COO group, where R′, identical or different, represents a hydrogen atom or an alkaline or alkaline earth metal, preferably R′ is H, preferably R.sup.2 and R.sup.3, identical or different, represent an OH or NH.sub.2 group.

Compositions are obtained by mixing at least one oligomer A1, which is obtained by copolymerizing at least two monomers functionalized by diol functions with at least one second monomer, with at least one compound A2 having at least two boron ester functions. The compositions exhibit very varied rheological properties depending on the proportion of the compounds A1 and A2 used. A composition is also obtained by mixing at least one lubricating oil with such a composition of associative and exchangeable polymers, and the use of this composition to lubricate a mechanical part.

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 crankcase lubricating oil composition for the crankcase of a spark-ignited or compression-ignited internal combustion engine, comprising a magnesium-containing detergent, in an amount sufficient to provide from 200-4000 ppm magnesium to the lubricating oil composition, in combination with an oil-soluble or oil-dispersible molybdenum compound in an amount sufficient to provide from 600-1500 ppm molybdenum atoms to the lubricating oil composition, and with an oil-soluble or oil-dispersible boron-containing compound in an amount sufficient to provide from 200-600 ppm boron atoms to the lubricating oil composition to improve the friction and fuel economy performance.

Friction modifier and compositions containing the friction modifier as a fuel additive are provided. Methods for improving fuel efficiency using these compositions are also provided.

A composition is obtained by mixing at least one oligomer A1, which is obtained by copolymerizing at least two monomers functionalized by diol functions with at least one second monomer, with at least one compound A2 having at least two boron ester functions. The compositions exhibit very varied rheological properties depending on the proportion of the compounds A1 and A2 used. A composition is also obtained by mixing at least one lubricating oil with such a composition of associative and exchangeable polymers, and the use of this composition to lubricate a mechanical part.

A lubricant composition includes a polyalkylene glycol base oil component in an amount of at least about 60 parts by weight based on 100 parts by weight of the lubricant composition. The lubricant composition has a kinematic viscosity at 100° C. of from about 4 to about 50 cSt and a kinematic viscosity at 40° C. of from about 20 to about 700 cSt, each measured in accordance with ASTM D445.

The present invention provides a lubricating oil composition for two-wheeled vehicles, which is able to not only suppress a lowering of fatigue life of engine parts while making fuel saving properties (in particular, fuel saving properties at the time of low speed) favorable but also make clutch friction characteristics of two-wheeled vehicles favorable. The present invention is concerned with a lubricating oil composition for two-wheeled vehicles, including a base oil (A) having a viscosity index of 120 or more, an ethylene-propylene copolymer (B), and a metal-based detergent (C), wherein the content of the ethylene-propylene copolymer (B) is 0.30% by mass or more on the basis of the whole amount of the lubricating oil composition; the metal-based detergent (C) contains a calcium phenate (C1) and a calcium sulfonate (C2), and a mass ratio of the content (Ca.sub.1) of the calcium phenate (C1) as expressed in terms of a calcium atom to the content (Ca.sub.2) of the calcium sulfonate (C2) as expressed in terms of a calcium atom is satisfied with a relation of (1.0≤Ca.sub.1/Ca.sub.2); and the lubricating oil composition has a kinematic viscosity at 100° C. is less than 9.3 mm.sup.2/s and an HTHS viscosity at 150° C. is 2.9 mPa.Math.s or more.

A fuel-saving-type engine oil composition is provided that exhibits a satisfactory friction-reducing effect in a low-viscosity engine oil without being constrained by, for example, high temperatures, low temperatures, low loads, or high loads. The engine oil composition includes: an engine oil having a low-temperature viscosity of from 0 to 10 in SAE viscosity grades and a high-temperature viscosity of from 4 to 20 in the SAE viscosity grades; and a molybdenum compound (A) represented by the following general formula (1): ##STR00001##
where R.sup.1 to R.sup.4 each independently represent a hydrocarbon group having 4 to 18 carbon atoms, and not all of R.sup.1 to R.sup.4 represent the same group, and when R.sup.1 and R.sup.2 represent the same group, R.sup.3 and R.sup.4 do not represent the same group, and X.sup.1 to X.sup.4 each independently represent a sulfur atom or an oxygen atom.

Provided are: a lubricating oil composition containing a mineral oil (A) having a kinematic viscosity at 40° C. of 5 to 15 mm.sup.2/s and a flash point of 180° C. or higher, a synthetic oil (B) having a kinematic viscosity at 40° C. of 5 to 15 mm.sup.2/s and a flash point of 190° C. or higher, an amide compound (C) and a polyol ester compound (D), which has a low viscosity and fuel saving performance, which can be used in high-temperature environments, and which has excellent gear anti-seizing property and anti-shudder performance; and a lubrication method and a transmission using the lubricating oil composition.