Lubricating oil compositions

Abstract

A lubricating oil composition comprising (a) a major amount of an oil of lubricating viscosity, (b) an ashless dispersant, (c) at least one metal-containing detergent, (d) an antioxidant, and (e) an anti-wear agent, wherein the lubricating oil composition is free of any zinc dialkyl dithiophosphate compound and is substantially free of any phosphorus content is disclosed.

Description

BACKGROUND OF THE INVENTION[0001]1. Technical Field[0002]The present invention generally relates to lubricating oil compositions for reducing wear in engines.[0003]2. Description of the Related Art[0004]Automobile spark ignition and diesel engines have valve train systems including, for example, valves, cams and rocker arms, which present special lubrication concerns. It is extremely important that the lubricant, i.e., the engine oil, protects these parts from wear. It is also important for the engine oils to suppress the production of deposits in the engines. Such deposits are produced from non-combustibles and incomplete combustion of hydrocarbon fuels (e.g., gasoline and diesel fuel oil) and by the deterioration of the engine oil employed.[0005]Engine oils typically use a mineral oil or a synthetic oil as a base oil. However, simple base oils alone do not provide the necessary properties to provide the necessary wear protection, deposit control, etc., required to protect internal...

AI Technical Summary

Benefits of technology

[0011]In accordance with a second embodiment of the present invention, a lubricating oil composition is provided comprising (a) a major amount of an oil of lubricating viscosity, (b) an ashless dispersant, (c) at least one metal-containing detergent, (d) an antioxidant, and (e) an anti-wear agent, wherein the lubricating oil composition is free of any zinc dialkyl dithiophosphate compound and is substantially free of any phosphorus content, and further wherein the lubricating oil composition has a wear reducing property greater than that of a corresponding lubricating oil composition in which a zinc dialkyl dithiophosphate compound is present therein.

[0012]In accordance with a third embodiment of the present invention, a method for improving the wear reducing properties of a lubricating oil composition is provided comprising the step of forming a lubricating oil composition comprising (a) a major amount of an oil of lubricating viscosity, (b) an ashless dispersant, (c) at least one metal-containing detergent, (d) an antioxidant, and (e) an anti-wear agent, wherein the lubricating oil composition is free of any zinc dialkyl dithiophosphate compound and is substantially free of any phosphorus content.

[0013]In accordance with a fourth embodiment of the present invention, there is provided a method of reducing wear in an internal combustion engine which comprises operating the internal combustion engine with a lubricating oil composition comprising (a) a major amount of an oil of lubricating viscosity, (b) an ashless dispersant, (c) at least one metal-containing detergent, (d) an antioxidant, and (e) an anti-wear agent, wherein the lubricating oil composition is free of any zinc dialkyl dithiophosphate compound and is substantially free of any phosphorus content.

[0015]The lubricating oil composition of the present invention advantageously possesses improved wear reducing properties while containing no zinc dialkyl dithiophosphate compound as compared to a corresponding lubricating oil composition in which a zinc dialkyl dithiophosphate compound is present therein. This is unexpected as zinc dialkyl dithiophosphate is a known antiwear agent typically used in lubricating oil compositions. In addition, the improved wear reducing properties can be achieved with the lubricating oil compositions of the present invention while also employing relatively low levels or free of any phosphorus content and relatively low levels of sulfur.

Problems solved by technology

However, simple base oils alone do not provide the necessary properties to provide the necessary wear protection, deposit control, etc., required to protect internal combustion engines.

However, a problem associated with the use of zinc dialkyldithiophosphate is that their phosphorus and sulfur derivatives poison the catalyst components of the catalytic converters.

As previously mentioned, these catalyst components are poisoned by the phosphorus and sulfur components, or the phosphorus and sulfur decomposition product of the zinc dialkyldithiophosphate; and accordingly, the use of engine oils containing phosphorus and sulfur additives may substantially reduce the life and effectiveness of catalytic converters.

It is widely believed that lowering these limits may have a serious impact on engine performance, engine wear, and oxidation of engine oils.

However, simply decreasing the amount of zinc dialkyldithiophosphate presents problems because this necessarily lowers the antiwear properties and oxidation inhibition properties of the lubricating oil.

Accordingly, as demand for further decrease of the phosphorus content and a limit on the sulfur content of lubricating oils is very high, this reduction cannot be satisfied by the present measures in practice and still meet the severe antiwear properties required of today's engine oils.

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