Disclosed is a lubricating oil composition for low-friction sliding materials, which is used in a sliding mechanism where a DLC film containing hydrogen in an amount of from 5 atom % to 50 atom % is formed on at least one sliding surface. The lubricating oil composition contains, in the lubricant base oil therein and based on the total amount of the composition, (A) an organic zinc dithiophosphate in an amount of from 0.005% by mass to 0.12% by mass in terms of the phosphorus concentration therein, (B) an amine-based friction-reducing agent in an amount of from 0.05% by mass to 5.0% by mass, and (C) an alkaline earth metal salicylate-based detergent and/or an alkaline earth metal sulfonate-based detergent in an amount of from 0.05% by mass to 0.5% by mass in terms of the alkaline earth metal concentration therein, wherein the component (A) contains, based on the total amount of the composition, a zinc primary dialkyldithiophosphate in an amount of from 0.005% by mass to 0.05% by mass in terms of the phosphorus concentration therein.

A process for producing a borated polyalkenyl succinimide dispersant composition in which the boron is incorporated primarily as cyclic metaboric acid moieties and the equivalents of boron incorporated per equivalent of nitrogen in the succinimide carrier is greater than 2; in which process a slurry of orthoboric acid is added to a polyalkenyl succinimide to form a reaction mixture, which reaction mixture is then heated under conditions (at a temperature and pressure and for a time) sufficient to remove from the reaction mixture from about 0.8 to about 1.2 moles of water of reaction per mole of boric acid charged.

A process for producing a borated polyalkenyl succinimide dispersant composition in which the boron is incorporated primarily as cyclic metaboric acid moieties and the equivalents of boron incorporated per equivalent of nitrogen in the succinimide carrier is greater than 2; in which process a slurry of orthoboric acid is added to a polyalkenyl succinimide to form a reaction mixture, which reaction mixture is then heated under conditions (at a temperature and pressure and for a time) sufficient to remove from the reaction mixture from about 0.8 to about 1.2 moles of water of reaction per mole of boric acid charged.

The lubricating oil composition of the present invention contains, together with a base oil, a viscosity index improver (A) including a comb-shaped polymer (A1), a detergent dispersant (B) including an alkali metal borate (B1) and an organometallic compound (B2) containing a metal atom selected from an alkali metal atom and an alkaline earth metal atom, and a friction modifier (C) including a molybdenum-containing friction modifier, with the total content of an alkali metal atom and an alkaline earth metal atom being 2,000 mass ppm or less. The lubricating oil composition of the present invention has excellent detergency, fuel saving properties, and LSPI-preventing properties.

The lubricating oil composition of the present invention contains, together with a base oil, a viscosity index improver (A) including a comb-shaped polymer (A1), a detergent dispersant (B) including an alkali metal borate (B1) and an organometallic compound (B2) containing a metal atom selected from an alkali metal atom and an alkaline earth metal atom, and a friction modifier (C) including a molybdenum-containing friction modifier, with the total content of an alkali metal atom and an alkaline earth metal atom being 2,000 mass ppm or less. The lubricating oil composition of the present invention has excellent detergency, fuel saving properties, and LSPI-preventing properties.

Lubricating oil compositions may include a base oil, a succinimide compound, and a thioheterocyclic compound. Such compositions may have a sulfur content of 0.10 mass % to 1.00 mass % based on a total amount of the composition. A phosphorus content represented by P in mass % and a sulfated ash content represented by M in mass %, based on the total amount of such compositions, may satisfy any of conditions A to C: condition A: P<0.03, and M<0.3; condition B: P<0.03 and 0.3≦M≦0.6; and condition C: 0.03≦P≦0.06 and M<0.3.

Lubricating oil compositions may include a base oil, a succinimide compound, and a thioheterocyclic compound. Such compositions may have a sulfur content of 0.10 mass % to 1.00 mass % based on a total amount of the composition. A phosphorus content represented by P in mass % and a sulfated ash content represented by M in mass %, based on the total amount of such compositions, may satisfy any of conditions A to C: condition A: P<0.03, and M<0.3; condition B: P<0.03 and 0.3≦M≦0.6; and condition C: 0.03≦P≦0.06 and M<0.3.

A method for improving corrosion protection and friction coefficient in an engine or other mechanical component lubricated with a lubricating oil by using as the lubricating oil a formulated oil. The formulated oil has a composition comprising a lubricating oil base stock as a major component, and a mixture of (i) at least one organic molybdenum compound, and (ii) at least one borated ester, as a minor component. Corrosion protection and friction coefficient are improved as compared to corrosion protection and friction coefficient achieved using a lubricating oil containing a minor component other than the mixture of (i) at least one organic molybdenum compound, and (ii) at least one borated ester.

The use of berated dispersant, preferably in combination with polyalkylenyl succinic anhydrides, to stabilise an additive concentrate which includes a salicylate detergent and a nitrogen-free ashless organic friction modifier.

The invention provides a method of lubricating a compression-ignition internal combustion engine with a maximum laden mass over 2,700 kg comprising supplying to the engine a lubricating composition comprising: an oil of lubricating viscosity, a 300 TBN or higher alkaline earth metal sulphonate detergent having a metal ratio of 10 to 40, 0.1 wt % to 4 wt % of a borated polyisobutylene succinimide dispersant, wherein the polyisobutylene from which the borated polyisobutylene succinimide is derived has a number average molecular weight of 550 to 1150, and 0.1 wt % to 6 wt % of a polyisobutylene succinimide, wherein the polyisobutylene from which polyisobutylene succinimide is derived has a number average molecular weight of 1550 to 2500, 0 wt % to 0.2 wt % of a phenolic based detergent, wherein the total amount of soap delivered by the alkaline earth metal sulphonates (typically calcium sulphonate) is 0.4 to 1 wt % of the lubricating composition, and wherein the lubricating composition has a sulphated ash content of not more than 1.5 wt %.