Solid anti-friction devices – materials therefor – lubricant or se – Lubricants or separants for moving solid surfaces and... – Nitrogen and heavy metal – or nitrogen and aluminum – in the...
Reexamination Certificate
1999-05-19
2001-10-09
Medley, Margaret (Department: 1714)
Solid anti-friction devices, materials therefor, lubricant or se
Lubricants or separants for moving solid surfaces and...
Nitrogen and heavy metal, or nitrogen and aluminum, in the...
C508S364000, C508S365000, C508S371000, C508S391000, C508S545000
Reexamination Certificate
active
06300291
ABSTRACT:
The present invention relates to lubricating oil compositions. More particularly, the present invention relates to lubricating oil compositions, which exhibit improvements in low temperature valve train wear performance, fuel economy and fuel economy retention properties.
BACKGROUND OF THE INVENTION
Additives have been used by many companies to try to improve engine performance. An additive or additive package may be used for a variety of purposes, such as detergency, reducing engine wear, stability against heat and oxidation, reducing oil consumption, corrosion inhibition, to act as a dispersant, and to reduce friction loss. Reducing friction loss is of great interest because of its impact on fuel economy performance. As such, friction modifiers have been given much attention.
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 is useful as a lubricant additive. In particular, molybdenum provides enhanced fuel economy in gasoline or diesel fueled engines, including both short and long term fuel economy (i.e., fuel economy retention properties). The prior proposals typically use molybdenum at levels greater than 350 ppm up to 2,000 ppm in additive packages, which contain one or more detergents, anti-wear agents, dispersants, friction modifiers, and the like.
Durability of engine lubricants is becoming an important issue. Today's lubricating oils quickly lose their ability to provide beneficial enhancements to engine performance. This makes it necessary to frequently change the engine's oil. As such oil consumption and maintenance costs increase, leaving car owners with an undesirable burden.
To address this problem, the present inventors have developed a lubricating oil composition that provides initial engine performance benefits and retention of those benefits for a longer period of time than with oils currently available in the marketplace. The composition is less volatile, which enables a greater percentage of the lubricating oil composition to remain in the engine over time. This leads to an improvement in fuel economy and fuel economy retention. Moreover, less maintenance is required, since drainage intervals are extended.
The present inventors have also found that low temperature valve train wear performance, fuel economy and fuel economy retention properties, can be improved to meet the requirements of the next generation of motor oil certification such as the proposed ILSAC GF-3 standards (International Lubricants Standardization and Approval Committee), using much lower levels of molybdenum than currently required in conventional additive packages.
SUMMARY OF THE INVENTION
The present invention concerns a lubricating oil composition which exhibits improved low temperature anti-wear performance and improved fuel economy and fuel economy retention properties, the composition comprising: (a) an oil of lubricating viscosity having a viscosity index of at least 95; (b) at least one calcium detergent; (c) at least one oil soluble molybdenum compound; (d) at least one nitrogen containing friction modifier, and (e) at least one zinc dihydrocarbyldithiophosphate compound. The composition has a NOACK volatility of about 15.5 wt. % or less, and contains from about 0.058 to 0.58 wt. % calcium from the calcium detergent, molybdenum in an amount up to about 350 ppm from a molybdenum compound, and phosphorus in an amount up to about 0.1 wt. % from the zinc dihydrocarbyldithiophosphate. The composition may be prepared by the admixture of the ingredients and such compositions are a further embodiment of this invention.
In addition, the present invention encompasses methods for improving the fuel economy and fuel economy retention properties of an engine and improving the anti-wear properties of an engine, the method comprising the steps of adding the lubricating oil composition of this invention to an engine and operating the engine.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The lubricating oil compositions of this invention require; (a) an oil of lubricating viscosity having a viscosity index of at least 95; (b) at least one calcium detergent; (c) at least one oil soluble molybdenum-containing compound; (d) at least one nitrogen containing friction modifier; and (e) at least one zinc dihydrocarbyldithiophosphate compound.
Oil of Lubricating Viscosity
The oil of lubricating viscosity may be selected from a wide variety of base stocks including natural oils, synthetic oils, or mixtures thereof. Examples of suitable base stocks may be found in one or more of the base stock groups, or mixtures of said base stock groups, set forth in the American Petroleum Institute (API) publication “Engine Oil Licensing and Certification System,” Industry Services Department, Fourteenth Edition, December 1996, Addendum 1, December 1998.
a) Group I base stocks contain less than 90 percent saturates and/or greater than 0.03 percent sulfur and have a viscosity index greater than or equal to 80 and less than 120 using the test methods specified in Table A below.
b) Group II base stocks contain greater than or equal to 90 percent saturates and less than or equal to 0.03 percent sulfur and have a viscosity index greater than or equal to 80 and less than 120 using the test methods specified in Table A below.
c) Group III base stocks contain greater than or equal to 90 percent saturates and less than or equal to 0.03 percent sulfur and have a viscosity index greater than or equal to 120 using the test methods specified in Table A below.
d) Group IV base stocks are polyalphaolefins (PAO).
e) Group V base stocks include all other base stocks not included in Groups I, II, III, or IV.
TABLE A
Analytical Methods for Testing Base Stocks
Property
Test Method
Saturates
ASTM D2007
Viscosity Index
ASTM D2270
Sulfur
ASTM D2622, D4292,
D4927, or D3120
The oil of lubricating viscosity used in this invention should have a viscosity index of at least 95, preferably at least 100. Preferred oils are (a) base oil blends of Group III base stocks with Group I or Group II base stocks, where the combination has a viscosity index of at least 110; or (b) Group III base stocks or blends of more than one Group III base stock.
Calcium Detergent
The present invention requires the presence of at least one calcium detergent. Detergents aid in reducing deposits that build up in an engine and act as an acid neutralizer or rust inhibitor. This in turn reduces engine wear and corrosion.
The calcium detergent used in this invention may be neutral or overbased and may be derived from phenates, salicylates, sulfonates, or mixtures thereof, with calcium sulfonates being particularly preferred. Preferably, the detergent will be overbased, that is the Total Base Number (TBN) will be at least 1 00 but usually between 100 and 500, more preferably between 150 and 450, and most preferably between 200 and 400. The most preferred detergent for use in this invention is an overbased calcium sulfonate having a TBN between 200 and 400.
The process of overbasing a metal detergent means that a stoichiometric excess of the metal is present over what is required to neutralize the anion of the salt. It is the excess metal from overbasing that has the effect of neutralizing acids which may build up.
In the present invention, overbased calcium sulfonate detergents may be derived from the salt of an oil soluble sulfonic acid, where a mixture of an oil soluble sulfonate or alkaryl sulfonic acid is combined with calcium and heated to neutralize the sulfonic acid that is present. This forms a dispersed carbonate complex by reacting the excess calcium with carbon dioxide. The sulfonic acids typically are obtained by the sulfonation of alkyl substituted aromatic hydrocarbons such as those obtained from the fractionation of petroleum or by the alkylation of aromatic hydrocarbons. Examples include those obtained by alkylating benzene, toluene, xylene, naphthalene, diphenyl or their halogen derivatives such as chlorobenz
Bell Ian A. W.
Bidwell Thomas R.
Farnsworth Gordon R.
Hartley Rolfe J.
Miyoshi Taisuke
Infineum USA L.P.
Medley Margaret
Toomer Cephia D.
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