Method for Preventing or Reducing Low Speed Pre-Ignition in Direct Injected Spark-Ignited Engines with Molybdenum-Containing Lubricant Compositions

This application is a continuation application of and claims priority to PCT/US2023/076005 filed Oct. 4, 2023, which claims the benefit of U.S. Provisional Patent Application No. 63/378,599 filed Oct. 6, 2022, the entire content of which is incorporated herein by reference.

This disclosure relates to a lubricant composition for a direct injected, boosted, spark-ignited internal combustion engine that contains molybdenum-containing compounds and calcium detergents. This disclosure also relates to a method for preventing or reducing low speed pre-ignition in an engine lubricated with a formulated oil.

Modern engine designs are being developed to improve fuel economy without sacrificing performance or durability. Historically, gasoline was port-fuel injected (PFI), that is, injected through the air intake and entering the combustion chamber via the air intake valve. Gasoline direct injection (GDI) involves direct injection of gasoline into the combustion chamber.

In certain situations, the internal combustion engine may exhibit abnormal combustion. Abnormal combustion in a spark-initiated internal combustion engine may be understood as an uncontrolled explosion occurring in the combustion chamber as a result of ignition of combustible elements therein by a source other than the igniter.

Pre-ignition may be understood as an abnormal form of combustion resulting from the ignition of the air-fuel mixture prior to ignition by the igniter. Anytime the air-fuel mixture in the combustion chamber is ignited prior to ignition by the igniter, such may be understood as pre-ignition.

Without being bound to a particular theory, traditionally, pre-ignition has occurred during high-speed operation of an engine when a particular point within the combustion chamber of a cylinder may become hot enough during high-speed operation of the engine to effectively function as a glow plug (e.g., overheated spark plug tip, overheated burr of metal) to provide a source of ignition which causes the air-fuel mixture to ignite before ignition by the igniter.

Such pre-ignition may be more commonly referred to as hot-spot pre-ignition and may be inhibited by simply locating the hot-spot and eliminating it.

More recently, vehicle manufacturers have observed intermittent abnormal combustion in their production of turbocharged gasoline engines, particularly at low speeds and medium-to-high loads. More particularly, when operating the engine at speeds less than or equal to 3000 rpm and under a load with a break mean effective pressure (BMEP) of greater than or equal to 10 bars, a condition which may be referred to as low-speed pre-ignition (LSPI) may occur in a random and stochastic fashion. Moreover, the propensity at which LSPI occurs has been linked to engine oil formulation, with an increasing number of LSPI events as the engine oil ages.

Although some engine knocking and pre-ignition problems can be and are being resolved through the use of new engine technology, such as electronic controls and knock sensors, and through the optimization of engine operating conditions, there is a role for lubricant compositions which can decrease or prevent the problem.

The presently disclosed engine oil lubricant is suitable for reducing, inhibiting, or even eliminating LSPI events in direct injection engines by operating the engines with a lubricant that contains a molybdenum compound. Typical engine oil designed to reduce LSPI events perform well at the beginning of its use but its performance falls off drastically over time. By distinct contrast, the disclosed engine oil lubricant is particularly suitable for maintaining LSPI reducing capacity during its normal use life.

In one aspect, the present disclosure provides a method for reducing or preventing low speed pre-ignition (LSPI) in a direct-injected, boosted, spark-ignited, internal combustion engine, said method comprising the step of lubricating the engine with a used or aged lubricant composition comprising:

For example, the molybdenum-containing compounds are oil soluble or oil dispersible molybdenum compounds including molybdenum-amine complexes, molybdenum dithiocarbamates, molybdenum dithiophosphates, and the like, and combinations thereof.

In certain embodiments, the one or more molybdenum-containing compounds, are in an amount providing the lubricant composition with at least about 850 ppm of molybdenum, based upon the total weight of the composition; and the one or more calcium detergents are in an amount providing the lubricant composition with at least about 1800 ppm of calcium, based upon the total weight of the composition.

In other embodiments, the one or more molybdenum-containing compounds are in an amount providing the lubricant composition with about 100 ppm to about 850 ppm of molybdenum, based upon the total weight of the composition; and the one or more calcium detergents are in an amount providing the lubricant composition with about 1000 to about 1450 ppm of calcium, based upon the total weight of the composition.

To define more clearly the terms used herein, the following definitions are provided. Unless otherwise indicated, the following definitions are applicable to this disclosure. If a term is used in this disclosure but is not specifically defined herein, the definition from the IUPAC Compendium of Chemical Terminology can be applied, as long as that definition does not conflict with any other disclosure or definition applied herein or render indefinite or non-enabled any claim to which that definition is applied. To the extent that any definition or usage provided by any document incorporated herein by reference conflicts with the definition or usage provided herein, the definition or usage provided herein controls.

While compositions and methods are described in terms of “comprising” various components or steps, the compositions and methods can also “consist essentially of” or “consist of” the various components or steps, unless stated otherwise.

The terms “a,” “an,” and “the” are intended to include plural alternatives, e.g., at least one. The terms “including”, “with”, and “having”, as used herein, are defined as comprising (i.e., open language), unless specified otherwise.

Various numerical ranges are disclosed herein. When Applicant discloses or claims a range of any type, Applicant's intent is to disclose or claim individually each possible number that such a range could reasonably encompass, including end points of the range as well as any sub-ranges and combinations of sub-ranges encompassed therein, unless otherwise specified. For example, all numerical end points of ranges disclosed herein are approximate, unless excluded by proviso.

A “major amount” means in excess of 50 wt. % of a composition.

A “minor amount” means less than 50 wt. % of a composition.

As used in connection with metallic detergents, the term “overbased” is used to designate metal salts in which the metal is present in stoichiometrically larger amounts than the organic radical.

As referred to herein, the term “ppm” means parts per million by weight, based on the total weight of the lubricant composition.

The “metal content” of the lubricant composition or the detergent component, for example magnesium content, calcium content or total metal content (i.e., the sum of all individual metal contents), is measured by ASTM D4951.

The term “used” or “aged” with respect to a lubricant composition means that the lubricant is not fresh. Used or aged lubricant composition will generally have oxidation, nitration, neutralization, fuel dilution, soot, and/or wear levels that correspond to the aging of this composition under the actual conditions of use. In certain embodiments, the used lubricant composition is used in the course of at least one oil change interval or over a distance travelled by the vehicle of at least about 3000 miles, 4000 miles, 5000 miles, 6000 miles, 7000 miles, or 8000 miles. In certain embodiments, the used lubricant composition is used over a distance travelled by the vehicle of about 3000 to about 20,000 miles, about 4000 to about 20,000 miles, about 5000 to about 20,000 miles, about 6000 to about 20,000 miles, about 7000 to about 20,000 miles, about 8000 to about 20,000 miles, about 3000 to about 15,000 miles, about 4000 to about 15,000 miles, about 5000 to about 15,000 miles, about 6000 to about 15,000 miles, about 7000 to about 15,000 miles, about 8000 to about 15,000 miles, about 3000 to about 10,000 miles, about 4000 to about 10,000 miles, about 5000 to about 10,000 miles, about 6000 to about 10,000 miles, about 7000 to about 10,000 miles, or about 8000 to about 10,000 miles.

In some embodiments, the used or agent lubricant composition has been used or aged for at least 1,000 miles such as for at least 2,000 miles, at least 3,000 miles, at least 4,000 miles, at least 5,000 miles, at least 6,000 miles, at least 7,000 miles, at least 8,000 miles, at least 9,000 miles, or at least 10,000.

In certain embodiments, the used or aged properties of a lubricant composition may be simulated for testing purposes, i.e., a lubricant composition may be artificially aged by simulating the conditions of use in an engine. For example, an artificially aged lubricant composition for testing may be produced by iron-catalyzed oxidation at a temperature in the range of about 150° C. to 170° C. for a period of about 110 to 150 hours, according the GFC Lu-43A-11 method. In certain embodiments, the used or aged properties of a lubricant composition may be simulated, for example as described in Example 6, to provide a lubricant composition comparable to a lubricant composition used over a desired distance travelled, for example 5000 miles, under normal driving conditions.

The term “boosting” is used throughout the specification. Boosting refers to running an engine at higher intake pressures than in naturally aspirated engines. A boosted condition can be reached by use of a turbocharger (driven by exhaust) or a supercharger (driven by the engine).

Using smaller engines that provide higher power densities has allowed engine manufacturers to provide excellent performance while reducing frictional and pumping losses. This is accomplished by increasing boost pressures with the use of turbochargers or mechanical superchargers, and by down-speeding the engine by using higher transmission gear ratios allowed by higher torque generation at lower engine speeds. However, higher torque at lower engine speeds has been found to cause LSPI events, resulting in extremely high cylinder peak pressures, which can lead to catastrophic engine failure. The possibility of LSPI prevents engine manufacturers from fully optimizing engine torque at lower engine speed in such smaller, high-output engines.

The terms “oil soluble” or “oil dispersible” means that an amount needed to provide the desired level of activity or performance can be incorporated by being dissolved, dispersed or suspended in an oil of lubricating viscosity. Usually, this means that at least about 0.001% by weight of the material can be incorporated in a lubricant composition. For a further discussion of the terms oil soluble and dispersible, particularly “stably dispersible”, see U.S. Pat. No. 4,320,019 which is expressly incorporated herein by reference for relevant teachings in this regard.

The term “sulfated ash” as used herein refers to the non-combustible residue resulting from detergents and metallic additives in lubricant. Sulfated ash may be determined using ASTM Test D874.

The term “Total Base Number” or “TBN” as used herein refers to the amount of base equivalent to milligrams of KOH in one gram of sample. Thus, higher TBN numbers reflect more alkaline products, and therefore a greater alkalinity. TBN was determined using ASTM D 2896 test.

Unless otherwise specified, all percentages are in weight percent.

The term “alkyl”, as used herein, unless otherwise specified, includes a saturated straight, branched, cyclic, primary, secondary, or tertiary hydrocarbon of Cto C. The term includes both substituted and unsubstituted alkyl groups. Moieties with which the alkyl group can be substituted are selected from the group consisting of hydroxyl, halo (F, Cl, Br, I), amino, alkylamino, arylamino, alkoxy, aryloxy, nitro, cyano, sulfonic acid, sulfate, phosphonic acid, phosphate, or phosphonate, either unprotected, or protected as necessary, as known to those skilled in the art, for example, as taught in Greene, et al., Protective Groups in Organic Synthesis, John Wiley and Sons, Second Edition, 1991, hereby incorporated by reference. When the alkyl group is said to be substituted with an alkyl group, this is used interchangeably with “branched alkyl group”. Specific examples of alkyls and/or substituted alkyls includes, but are not limited to, methyl, ethyl, propyl, isopropyl, n-butyl, iso-butyl, tert-butyl, n-pentyl, iso-pentyl, neopentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, isotridecyl, tetradecyl, hexadecyl, stearyl, icosyl, docosyl, tetracosyl, triacontyl, 2-ethylhexyl, 2-butyloctyl, 2-butyldecyl, 2-hexyloctyl, 2-hexyldecyl, 2-octyldecyl, 2-hexyldodecyl, 2-octyldodecyl, 2-decyltetradecyl, 2-dodecylhexadecyl, 2-hexadecyloctadecyl, 2-tetradecyloctadecyl, myristyl, palmityl and stearyl.

The term “cycloalkyl” or “cyclic alkyl” refers to a species of alkyl containing from 3 to 15 carbon atoms including one or more rings, without alternating or resonating double bonds between carbon atoms. The term includes both substituted and unsubstituted cycloalkyl groups. Moieties with which the cycloalkyl group can be substituted are selected from the group consisting of hydroxyl, halo (F, Cl, Br, I), amino, alkylamino, arylamino, alkoxy, aryloxy, nitro, cyano, sulfonic acid, sulfate, phosphonic acid, phosphate, or phosphonate, either unprotected, or protected as necessary, as known to those skilled in the art, for example, as taught in Greene, et al., Protective Groups in Organic Synthesis, John Wiley and Sons, Second Edition, 1991, hereby incorporated by reference. For example, cycloalkyls include but are not limited to cyclopropyl, cyclobutyl, cyclopentyl, and cyclohexyl. In certain embodiments, the cycloalkyl contains from 1 to 4 rings, which can be fused. In certain embodiments, the cycloalkyl group may contain one or more double bonds or triple bonds in one or more rings.

The term “alkenyl” includes a hydrocarbon radical straight, branched or cyclic containing from 2 to 10 carbon atoms and at least one carbon to carbon double bond. Examples of alkenyl groups include ethenyl, propenyl, butenyl and cyclohexenyl.

Although any processes and materials similar or equivalent to those described herein can be used in the practice or testing of the invention, the typical processes and materials are herein described.

All publications and patents mentioned herein are incorporated herein by reference for the purpose of describing and disclosing, for example, the constructs and methodologies that are described in the publications, which might be used in connection with the presently described invention. The publications discussed throughout the text are provided solely for their disclosure prior to the filing date of the present application. Nothing herein is to be construed as an admission that the inventors are not entitled to antedate such disclosure by virtue of prior invention.

The present disclosure generally relates to methods for reducing or preventing low speed pre-ignition (LSPI) in a direct-injected, boosted, spark-ignited, internal combustion engine in or during the course of an oil change interval. In another aspect, the present disclosure provides methods for maintain low speed pre-ignition reduction capacity of a used or aged lubricant composition in a direct-injected, boosted, spark-ignited, internal combustion engine. The lubricant compositions for use in the methods according to the invention comprise: (i) one or more oils of lubricating viscosity; (ii) one or more molybdenum-containing compounds, and (iii) one or more calcium detergents. The exemplary lubricant compositions are suitable for reducing, preventing, inhibiting or eliminating LSPI events in direct-injected, boosted, spark-ignited, internal combustion engines with used or aged lubricant compositions.

Lubricant compositions, which provide a reduction in LSPI when they are fresh or newly applied to the crankcase of the engine, can suffer degradation of such properties after use or aging. Preignition can be exacerbated by used or aged lubricant compositions. The Applicants have discovered that the lubricant compositions according to the embodiments retain their LSPI reduction capacity through use or aging, i.e., over the long term. Through the methods according to the invention, the exemplary lubricant compositions can be used to prevent or reduce LSPI in direct-injected, boosted, spark-ignited, internal combustion engines in a prolonged manner in the course of its use without substantial loss of performance. Use of the lubricant compositions according to the invention in place of comparative lubricant compositions, can reduce the need to change the lubricant composition in the engine for the purpose of reducing LSPI.

Low Speed Pre-Ignition is most likely to occur in direct-injected, boosted (turbocharged or supercharged), spark-ignited (gasoline) internal combustion engines that, in operation, generate a brake mean effective pressure (BMEP) level of at least about 15 bar (peak torque), at least about 18 bar, or at least about 20 bar, at engine speeds of from about 1500 to about 2500 rotations per minute (rpm), or from about 1500 to about 2000 rpm. As used herein, “brake mean effective pressure” or “BMEP” is defined as the work accomplished during one engine cycle, divided by the engine swept volume; the engine torque normalized by engine displacement. The word “brake” denotes the actual torque/power available at the engine flywheel, as measured on a dynamometer. Thus, BMEP is a measure of the useful power output of the engine.

In certain embodiments, the engine is operated at speeds between about 500 rpm and about 3000 rpm, about 800 rpm to about 2800 rpm, or about 1000 rpm to about 2600 rpm. Additionally, the engine may be operated with a brake mean effective pressure of about 10 bars to about 30 bars, about or about 12 bars to about 30 bars or about 12 bars to about 24 bars.

LSPI events, while comparatively uncommon, may be catastrophic in nature. Hence drastic reduction or even elimination of LSPI events during normal or sustained operation of a direct fuel injection engine is desirable.

In one embodiment, the method of the invention provides a reduction in the number of LSPI events of at least 10 percent, at least 20 percent, at least 30 percent, at least 50 percent, at least 60 percent, at least 70 percent, at least 80 percent, at least 90 percent, or at least 95 percent, compared to an oil or lubricant composition that does not contain the one or more molybdenum compounds and one or more calcium detergents according to the embodiments.

Therefore, in an aspect, the present disclosure provides a method for reducing or preventing LSPI in a direct-injected, boosted, spark-ignited, internal combustion engine, said method comprising the step of lubricating the engine with a used or aged lubricant composition comprising:

In one embodiment, the (ii) one or more molybdenum-containing compounds, are in an amount providing the lubricant composition with at least about 850 ppm of molybdenum, based upon the total weight of the composition; and the (iii) one or more calcium detergents are in an amount providing the lubricant composition with at least about 1800 ppm of calcium, based upon the total weight of the composition.

In another embodiment, wherein the (ii) one or more molybdenum-containing compounds are in an amount providing the lubricant composition with about 100 ppm to about 850 ppm of molybdenum, based upon the total weight of the composition; and the (iii) one or more calcium detergents are in an amount providing the lubricant composition with about 1000 to about 1450 ppm of calcium, based upon the total weight of the composition.

In certain embodiments, the (iii) one or more calcium detergents are in an amount providing the lubricant composition with less than about 3500 ppm, less than about 3000 ppm, less than about 2500 ppm, less than about 2400 ppm, less than about 2300 ppm, less than about 2200 ppm, less than about 2100 ppm, less than about 2000 ppm, less than about 1900 ppm, less than about 1800 ppm, less than about 1700 ppm, less than about 1600 ppm, less than about 1500 ppm, or less than about 1450 ppm of calcium, based upon the total weight of the composition.

In certain embodiments, the direct-injected, boosted, spark-ignited, internal combustion engine is a downsized engine or an engine that ranges in size from about 0.5 liters to about 3.6 liters.

In certain embodiments, the engine is a downsized turbocharged engine.

Certain embodiments provide methods for maintaining LSPI reduction capacity of a used or aged lubricant composition in a direct-injected, boosted, spark-ignited internal combustion engine, wherein the method comprises the step of lubricating the engine with the lubricant composition described herein.