A method for improving wear control of a steel surface lubricated with a lubricating oil through the generation of thick tribofilms. The method includes: (i) using as the lubricating oil a formulated oil, the formulated oil having a composition comprising at least one lubricating oil base stock as a major component; and at least one lubricating oil additive, as a minor component; and (ii) forming a tribofilm on the steel surface. In time-step tribofilm formation measurements of the lubricating oil by a mini-traction machine (MTM) at constant slide-to-roll ratio (SRR), the saturation traction coefficient (f.sub.s), which correlates to tribofilm thickness on the steel surface, is greater than about 0.11. In the method of this disclosure, elongation of timing chain due to wear of chain link pins is less than about 0.07%, as determined by Ford Chain Wear (FCW) test conducted in accordance with ILSAC GF-6 specification. The lubricating oils are useful in internal combustion engines.

A method for improving wear control of a steel surface lubricated with a lubricating oil through the generation of thick tribofilms. The method includes: (i) using as the lubricating oil a formulated oil, the formulated oil having a composition comprising at least one lubricating oil base stock as a major component; and at least one lubricating oil additive, as a minor component; and (ii) forming a tribofilm on the steel surface. In time-step tribofilm formation measurements of the lubricating oil by a mini-traction machine (MTM) at constant slide-to-roll ratio (SRR), the saturation traction coefficient (f.sub.s), which correlates to tribofilm thickness on the steel surface, is greater than about 0.11. In the method of this disclosure, elongation of timing chain due to wear of chain link pins is less than about 0.07%, as determined by Ford Chain Wear (FCW) test conducted in accordance with ILSAC GF-6 specification. The lubricating oils are useful in internal combustion engines.

A method for improving wear control, while maintaining or improving deposit control and cleanliness, 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 including a lubricating oil base stock as a major component, and specific combinations of low soap detergents, dispersants, and/or mixtures thereof, as a minor component. The low soap detergents include alkaline earth metal salicylates, alkaline earth metal sulfonates, or mixtures thereof, all having the same or different total base number (TBN). The total amount of soap delivered by the low soap detergent is less than 0.60 weight percent of the lubricating oil. The dispersants include borated and/or non-borated polyisobutylene succinimide (PIMA) having a basic nitrogen content of 1% or greater. The lubricating oils are useful in internal combustion engines.

A method for improving wear control, while maintaining or improving deposit control and cleanliness, 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 including a lubricating oil base stock as a major component, and specific combinations of low soap detergents, dispersants, and/or mixtures thereof, as a minor component. The low soap detergents include alkaline earth metal salicylates, alkaline earth metal sulfonates, or mixtures thereof, all having the same or different total base number (TBN). The total amount of soap delivered by the low soap detergent is less than 0.60 weight percent of the lubricating oil. The dispersants include borated and/or non-borated polyisobutylene succinimide (PIMA) having a basic nitrogen content of 1% or greater. The lubricating oils are useful in internal combustion engines.

A method for improving wear control of a steel surface lubricated with a lubricating oil through the generation of fast-forming tribofilms. The method includes: (i) using as the lubricating oil a formulated oil, the formulated oil having a composition comprising at least one lubricating oil base stock as a major component, and at least one detergent, as a minor component; and (ii) forming a tribofilm on the steel surface. The time for the tribofilm to reach 95% of its saturation coverage (t.sub.95,sat) on the steel surface is less than about 50 minutes, as determined by a high frequency reciprocating rig (HFRR) in accordance with a modified version of ASTM D6079. A lubricating oil including an ester base stock, an alkylated naphthalene base stock, or mixtures thereof, as a major component; and at least one detergent including an alkaline earth metal salicylate, an alkaline earth metal sulfonate, or mixtures thereof, as a minor component.

A method for improving wear control of a steel surface lubricated with a lubricating oil through the generation of fast-forming tribofilms. The method includes: (i) using as the lubricating oil a formulated oil, the formulated oil having a composition comprising at least one lubricating oil base stock as a major component, and at least one detergent, as a minor component; and (ii) forming a tribofilm on the steel surface. The time for the tribofilm to reach 95% of its saturation coverage (t.sub.95,sat) on the steel surface is less than about 50 minutes, as determined by a high frequency reciprocating rig (HFRR) in accordance with a modified version of ASTM D6079. A lubricating oil including an ester base stock, an alkylated naphthalene base stock, or mixtures thereof, as a major component; and at least one detergent including an alkaline earth metal salicylate, an alkaline earth metal sulfonate, or mixtures thereof, as a minor component.

A conductive lubricating oil composition including at least one lubricating base oil selected from the group consisting of compounds represented by the following General Formula (1) and compounds represented by the following General Formula (2), and at least one conductivity imparting agent selected from the group consisting of potassium trifluoromethanesulfonate, lithium trifluoromethanesulfonate, lithium nonafluorobutanesulfonate, lithium bis(trifluoromethanesulfonyl)imide, potassium bis(trifluoromethanesulfonyl)imide, and lithium tris(trifluoromethanesulfonyl)methide, in an amount of from 0.01% by mass to 1% by mass, and having a rate of change in conductivity after storage at 120 C. for 200 hours of 10% or less. The definitions of R.sup.1, R.sup.2, m and n in the formulae are as indicated in the specification. Cases of mn=2 are excluded.

##STR00001##

A conductive lubricating oil composition including at least one lubricating base oil selected from the group consisting of compounds represented by the following General Formula (1) and compounds represented by the following General Formula (2), and at least one conductivity imparting agent selected from the group consisting of potassium trifluoromethanesulfonate, lithium trifluoromethanesulfonate, lithium nonafluorobutanesulfonate, lithium bis(trifluoromethanesulfonyl)imide, potassium bis(trifluoromethanesulfonyl)imide, and lithium tris(trifluoromethanesulfonyl)methide, in an amount of from 0.01% by mass to 1% by mass, and having a rate of change in conductivity after storage at 120 C. for 200 hours of 10% or less. The definitions of R.sup.1, R.sup.2, m and n in the formulae are as indicated in the specification. Cases of mn=2 are excluded.

##STR00001##

The present in relates to a lubricating oil composition for sliding member having a coating film, the lubricating oil composition containing a base oil; (A) a zinc dialkyldithiophosphate; and (B) a metallic detergent, wherein the content of sulfur atom (S) is 2,800 ppm by mass or less on the basis of the whole amount of the lubricating oil composition, and a mass ratio of the content of sulfur atom (S) and the content of metal atom (BM) derived from the component (B) [(S)/(BM)] in the lubricating oil composition is 0.07 or more and 2.90 or less.

The present in relates to a lubricating oil composition for sliding member having a coating film, the lubricating oil composition containing a base oil; (A) a zinc dialkyldithiophosphate; and (B) a metallic detergent, wherein the content of sulfur atom (S) is 2,800 ppm by mass or less on the basis of the whole amount of the lubricating oil composition, and a mass ratio of the content of sulfur atom (S) and the content of metal atom (BM) derived from the component (B) [(S)/(BM)] in the lubricating oil composition is 0.07 or more and 2.90 or less.