Lubricating oil compositions comprising a molybdenum compound and a zinc dialkyldithiophosphate

Provided herein are lubricating oil compositions comprising a base oil, an oil soluble molybdenum compound and a zinc dithiophosphate compound. Methods of making and using the lubricating oil compositions are also described.

Lubricating oil compositions used to lubricate internal combustion engines contain base oil of lubricating viscosity, or a mixture of such oils, and additives used to improve the performance characteristics of the oil. For example, additives are used to improve detergency, to reduce engine wear, to provide stability against heat and oxidation, to reduce oil consumption, to inhibit corrosion, to act as a dispersant, and to reduce friction loss. Some additives provide multiple benefits, such as dispersant-viscosity modifiers. Other additives, while improving one characteristic of the lubricating oil, have an adverse effect on other characteristics. Thus, to provide lubricating oil having optimal overall performance, it is necessary to characterize and understand all the effects of the various additives available, and carefully balance the additive content of the lubricant.

It has been proposed in many patents and articles (for example, U.S. Pat. Nos. 4,164,473; 4,176,073; 4,176,074; 4,192,757; 4,248,720; 4,201,683; 4,289,635; and 4,479,883) that oil-soluble molybdenum compounds are useful as lubricant additives. In particular, the addition of molybdenum compounds to oil, particularly molybdenum dithiocarbamate compounds, provides the oil with improved boundary friction characteristics and bench tests demonstrate that the coefficient of friction of oil containing such molybdenum compounds is generally lower than that of oil containing organic friction modifiers. This reduction in coefficient of friction results in improved antiwear properties and may contribute to enhanced fuel economy in gasoline or diesel fired engines, including both short- and long-term fuel economy properties (i.e., fuel economy retention properties). To provide antiwear effects, molybdenum compounds are generally added in amounts introducing from about 350 ppm up to 2,000 ppm of molybdenum into the oil. molybdenum compounds are effective antiwear agents and may further provide fuel economy benefits, such molybdenum compounds are expensive relative to more conventional, metal-free (ashless) organic friction modifiers

Therefore, it is desirable to find a lubricating oil composition that provides improved fuel economy benefit; demonstrates excellent wear protection characteristics, is relatively low in cost.

Provided herein are lubricating oil compositions that provide an improved friction reduction. The lubricating oil compositions comprising

i) a major amount of a base oil,

ii) at least one oil-soluble molybdenum compound and

iii) a zinc dialkyldithiophosphate compound,

wherein the molybdenum content derived from the molybdenum compound is at least about 10 ppm based on the total weight of the lubricating oil composition and the phosphorus content derived from the zinc dialkyldithiophosphate compound is about 200 to 500 ppm based on the total weight of the lubricating oil composition.

In certain aspects, the base oil is present in an amount greater than about 40%, 50%, 60% or about 70% by weight of the lubricating oil compositions.

In certain embodiments, the lubricating oil composition disclosed herein further comprises at least one additive selected from the group consisting of antioxidants, antiwear agents, detergents, rust inhibitors, demulsifiers, friction modifiers, multi-functional additives, viscosity index improvers, pour point depressants, foam inhibitors, metal deactivators, dispersants, corrosion inhibitors, lubricity improvers, thermal stability improvers, anti-haze additives, dyes, markers, and combinations thereof.

Also provided herein are methods of making lubricating oil compositions. In one aspect, the methods comprise the step of mixing

i) a major amount of a base oil,

ii) at least one oil-soluble molybdenum compound and

iii) a zinc dialkyldithiophosphate compound,

wherein the molybdenum content derived from the molybdenum compound is at least about 10 ppm based on the total weight of the lubricating oil composition and the phosphorus content derived from the zinc dialkyldithiophosphate compound is about 200 to 500 ppm based on the total weight of the lubricating oil composition. In certain embodiments, the molybdenum compound and the zinc dialkyldithiophosphate compound used as described herein show synergy and resulting low friction coefficient in prototype GF-5 lubricating compositions.

Also provided herein are methods of lubricating a motor engine with a lubricating oil compositions provided herein. In one aspect, the methods comprise the step of operating the engine with the lubricating oil composition of provided herein.

Other embodiments will be in part apparent and in part pointed out hereinafter.