KR102366772B1 - Lubricant composition for direct injection engine - Google Patents

Abstract

The present invention relates to a method for reducing low speed pre-ignition events in a spark-ignition direct injection internal combustion engine by supplying a sump with a lubricant composition comprising a lubricating viscosity oil and an overbased sodium detergent. The metal overbased detergent may be selected from sulfonate detergents, phenate detergents and salicylate detergents, in particular sulfonate detergents having a metal ratio of at least 5.

Description

Lubricant composition for direct injection engine

The disclosed technology relates to lubricants for internal combustion engines, in particular lubricants for spark-ignition direct injection engines.

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

Under certain circumstances, an internal combustion engine may exhibit abnormal combustion. Abnormal combustion in spark-initiated internal combustion engines can be understood as an uncontrolled explosion that occurs in a combustion chamber as a result of ignition of a combustible element within the combustion chamber by a source other than an igniter.

Pre-ignition can be understood as an abnormal form of combustion resulting from the ignition of an 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, this may be understood as pre-ignition.

Without wishing to be bound by theory, traditionally, pre-ignition is one in which certain points within the combustion chamber of a cylinder become sufficiently hot during high-speed operation of the engine to provide a source of ignition that causes the air-fuel mixture to ignite prior to ignition by the igniter. Occurs during high-speed operation of the engine when functioning effectively as a glow plug (eg, overheated spark plug tip, overheated metal burr). Such pre-ignition may be more commonly referred to as a hot-spot pre-ignition and may be suppressed by simply finding and removing the hot spot.

More recently, vehicle manufacturers have observed intermittent abnormal combustion in the production of their turbocharged gasoline engines, particularly at low speeds and at medium to high loads. More particularly, when operating the engine under a load with a speed of 3,000 rpm or less and a brake mean effective pressure (BMEP) of 10 bar or more, a condition that may be referred to as low speed pre-ignition (LSPI) is very random and It can happen in a probabilistic way.

The disclosed technology provides a method of reducing, suppressing or even eliminating LSPI events in direct injection engines by operating the engine with a lubricant containing an overbased sodium detergent.

Summary of invention

The disclosed technology reduces low speed pre-ignition events in spark-ignited direct injection internal combustion engines comprising supplying to a sump a lubricant composition containing an oil of lubricating viscosity and an overbased sodium detergent provides a way to do it. The overbased sodium detergent may be selected from sulfonate detergents, phenate detergents and salicylate detergents, in particular sulfonate detergents, which will be present in the lubricating composition in an amount to deliver at least 25 ppm sodium by weight and up to 225 ppm sodium by weight. can .

The present invention provides a method for reducing low speed pre-ignition events in a spark-ignition direct injection internal combustion engine comprising supplying the engine with a lubricant composition comprising a lubricating viscosity base oil and a metal overbased detergent.

The present invention further provides the method described herein wherein the engine is operated under a load having a brake mean effective pressure (BMEP) of 10 bar or greater.

The present invention further provides the method described herein wherein the engine is operated at a speed of 3,000 rpm or less.

The present invention further provides the method described herein wherein the engine is fueled with a liquid hydrocarbon fuel, a liquid non-hydrocarbon fuel, or a mixture thereof.

The present invention further provides the method described herein wherein the engine is fueled with natural gas, liquefied petroleum gas (LPG), compressed natural gas (CNG), or mixtures thereof.

The invention further provides the methods described herein, wherein the overbased sodium detergent comprises one or more of a sulfonate detergent, a phenate detergent, a salicylate detergent, and combinations thereof.

The present invention provides that the lubricant composition further comprises at least one other additive selected from metal-containing detergents different from those of ashless dispersants, ashless antioxidants, phosphorus-containing anti-wear additives, friction modifiers, polymeric viscosity modifiers and overbased sodium detergents. Further provided are methods described herein.

The present invention further provides the method described herein, wherein the overbased sodium detergent comprises a sulfonate detergent.

The invention further provides the method described herein, wherein the overbased sodium detergent comprises a salicylate detergent.

The present invention further provides the method described herein wherein the overbased sodium detergent has a metal ratio of 5 to 30.

The present invention further provides the method described herein wherein the overbased sodium detergent is present in an amount of 0.2 to 8% by weight of the lubricant composition.

The present invention further provides the method described herein, wherein the lubricating composition further comprises a polyalkenyl succinimide dispersant in an amount of 0.5 to 4% by weight of the composition.

The present invention further provides the method described herein, wherein the lubricating composition comprises at least 50% by weight of a Group II base oil, a Group III base oil, or a mixture thereof.

The invention further provides the method described herein, wherein the overbased sodium detergent comprises a sulfur-linked phenate detergent.

The present invention further provides the method described herein, wherein the overbased sodium detergent is present in an amount to provide 0.1% to 0.9% by weight sulfate ash to the lubricating composition.

The invention further provides a method described herein for reducing the number of LSPI events by at least 10%.

The present invention further provides the method described herein wherein the slow pre-ignition event is reduced to less than 20 LSPI events per 100,000 burn events.

details

Various preferred features and embodiments will be described below by way of non-limiting example.

As indicated above, when operating the engine under a load with a speed of 3,000 rpm or less and a brake mean effective pressure (BMEP) of 10 bar or more, a low speed pre-ignition (LSPI) event may occur in the engine. there is. An LSPI event may consist of one or more LSPI combustion cycles, and may consist of multiple LSPI combustion cycles occurring in a generally continuous fashion or in alternating fashion with normal combustion cycles in between. Without wishing to be bound by theory, the LSPI is, for example, the top land interstitial volume of a piston, or a combination of oil drop(s) that may accumulate in the piston ring-land and ring-groove clearances or droplets of an oil-fuel mixture ( ), or combinations thereof. Lubricating oil may be transferred from under the oil control ring to the piston top land area due to abnormal movement of the piston ring. The in-cylinder pressure dynamics (compression and combustion pressures) at low speed and high load conditions are particularly pronounced at lower loads, due to strongly delayed combustion phasing and high boost and peak compressive pressures that can affect the ring motion dynamics. can be significantly different from the in-cylinder pressure of

At the loads described above, LSPIs, which may be accompanied by subsequent explosions and/or severe engine knocks, can cause serious damage to the engine very quickly (often within 1 to 5 engine cycles). An engine knock can occur with an LSPI given that multiple flames can exist after a normal spark from the igniter is provided. It is an object of the present invention to provide a method for inhibiting or reducing LSPI events comprising supplying an engine with a lubricant comprising a metal overbased detergent.

In one embodiment of the invention, the engine is operated at a speed of 500 rpm to 3000 rpm, or 800 rpm to 2800 rpm, or even 1000 rpm to 2600 rpm. In addition, the engine can be operated with a braking average effective pressure of 10 bar to 30 bar, or 12 bar to 24 bar.

Although relatively rare, LSPI events can be fatal in nature. Accordingly, a sharp reduction or even elimination of LSPI events during normal or sustained operation of direct fuel injection engines is desirable. In one embodiment, the method of the present invention causes there to be less than 20 LSPI events per 100,000 burn events or less than 10 LSPI events per 100.000 burn events. In one embodiment, there may be less than 5 LSPI events per 100.000 burn events, less than 3 LSPI events per 100.000 burn events; Or there may be 0 LSPI events per 100.000 burn events.

In one embodiment, the method of the present invention provides a reduction in the number of LSPI events of at least 10%, or at least 20%, or at least 30%, or at least 50%.

fuel

The method of the present invention comprises operating a spark-ignited internal combustion engine. In addition to engine operating conditions and lubricant composition, the composition of the fuel can affect LSPI events. In one embodiment, the fuel may include a fuel that is liquid at ambient temperature and useful for fueling a spark ignition engine, a fuel that is a gas at ambient temperature, or a combination thereof.

Liquid fuels are generally liquid at ambient conditions such as room temperature (20-30° C.). The fuel may be a hydrocarbon fuel, a non-hydrocarbon fuel, or a mixture thereof. The hydrocarbon fuel may be gasoline as defined by ASTM standard D4814. In an embodiment of the present invention, the fuel is gasoline, and in another embodiment, the fuel is lead gasoline, or unleaded gasoline.

The non-hydrocarbon fuel may be an oxygen-containing composition often referred to as an oxygenate comprising an alcohol, an ether, a ketone, an ester of a carboxylic acid, a nitroalkane, or mixtures thereof. Non-hydrocarbon fuels include, for example, methanol, ethanol, methyl t-butyl ether, methyl ethyl ketone, transesterified oils and/or fats from plants and animals such as rapeseed methyl ester and soybean methyl ester, and nitromethane. may include The mixture of hydrocarbon and non-hydrocarbon fuel may include, for example, gasoline and methanol and/or ethanol. In an embodiment of the present invention, the liquid fuel is a mixture of gasoline and ethanol, wherein the ethanol content is at least 5% by volume of the fuel composition, or at least 10% by volume of the composition, or at least 15% by volume of the composition, or 15 to 85% by volume of the composition %am. In one embodiment, the liquid fuel contains less than 15 vol % ethanol content, less than 10 vol % ethanol content, less than 5 vol % ethanol content, or is substantially free of ethanol (ie, less than 0.5 vol %). .

In some embodiments of the present invention, the fuel is 5000 ppm or less, 1000 ppm or less, 300 ppm or less, 200 ppm or less, 30 ppm or less, or 10 ppm or less sulfur by weight. content may have. In another embodiment, the fuel may have a sulfur content of from 1 to 100 ppm by weight. In one embodiment, the fuel is from about 0 ppm to about 1000 ppm, from about 0 to about 500 ppm, from about 0 to about 100 ppm, from about 0 to about 50 ppm, from about 0 to about 25 ppm, from about 0 to about 10 ppm, or about 0 to 5 ppm of alkali metals, alkaline earth metals, transition metals, or mixtures thereof. In another embodiment, the fuel contains 1 to 10 ppm by weight alkali metal, alkaline earth metal, transition metal, or mixtures thereof.

A gaseous fuel is generally a gas at ambient conditions such as room temperature (20-30° C.). Suitable gaseous fuels include natural gas, liquefied petroleum gas (LPG), compressed natural gas (CNG), or mixtures thereof. In one embodiment, the engine is fueled with natural gas.

The fuel composition of the present invention may further comprise one or more performance additives. Performance additives may be added to the fuel composition depending on several factors including the type of internal combustion engine and the type of fuel used in the engine, the quality of the fuel, and the service condition in which the engine is operating. In some embodiments, the added performance additive does not contain nitrogen. In another embodiment, the additional performance additive may contain nitrogen.

Performance additives include antioxidants such as hindered phenols or derivatives thereof and/or diarylamines or derivatives thereof; corrosion inhibitors such as alkenylsuccinic acid; and/or detergent/dispersion additives such as polyetheramines or nitrogen including, but not limited to, polyisobutylene (PIB) amine dispersants, Mannich detergents, succinimide dispersants, and their respective quaternary ammonium salts. containing detergents.

Performance additives may also include cold flow modifiers such as esterified copolymers of maleic anhydride and styrene and/or copolymers of ethylene and vinyl acetate; foam inhibitors such as silicone fluids; demulsifiers such as polyoxyalkylene and/or alkyl polyether alcohols; lubricating agents such as fatty carboxylic acids, ester and/or amide derivatives of fatty carboxylic acids, or ester and/or amide derivatives of hydrocarbyl substituted succinic anhydride; aromatic triazoles or derivatives thereof including but not limited to metal deactivators such as benzotriazoles such as tolyltriazole; and/or a valve seat recession additive such as an alkali metal sulfosuccinate salt. Additives may also include biocides, antistatic agents, deicing agents, glidants such as mineral oils and/or poly(alpha-olefins) and/or polyethers, and combustion modifiers such as octane or cetane modifiers.

The glidant may be a polyetheramine or a polyether compound. The polyether amine may be represented by the formula R[-OCH ₂ CH(R ¹ )] _n A, wherein R is a hydrocarbyl group, R ¹ is hydrogen, a hydrocarbyl group of 1 to 16 carbon atoms, and is selected from the group consisting of mixtures thereof, n is a number from 2 to about 50, and A is selected from the group consisting of —OCH ₂ CH ₂ CH ₂ NR ² R ² and —NR ³ R ³ , wherein each R ² is independently hydrogen or hydrocarbyl and each R ³ is independently hydrogen, hydrocarbyl or —[R ⁴ N(R ⁵ )] _p R ⁶ , wherein R ⁴ is C ₂ -C ₁₀ alkyl ren, R ⁵ and R ⁶ are independently hydrogen or hydrocarbyl, and p is a number from 1 to 7.

The glidant may be a polyether, which may be represented by the formula R ⁷ O[CH ₂ CH(R ⁸ )O] _q H, wherein R ⁷ is a hydrocarbyl group and R ⁸ is hydrogen, 1 to carbon atoms 16 hydrocarbyl groups, and mixtures thereof, and q is a number from 2 to about 50. The glidant may be a hydrocarbyl-terminated poly(-oxyalklene)aminocarbamate as described in US Pat. No. 5,503,644. The glidant may be an alkoxylate, wherein the alkoxylate comprises (i) a polyether containing at least two ester end groups; (ii) polyethers containing at least one ester group and at least one terminal ether group; or (iii) a polyether containing at least one ester group and at least one terminal amino group, wherein the terminal group is defined as a group located within 5 connecting carbon or oxygen atoms from the polymer terminus. A linkage is defined as the sum of the connecting carbon and oxygen atoms in a polymer or end group.

The fuel additive compositions and performance additives that may be present in the fuel compositions of the present invention are also known, optionally in combination with dicarboxylic acids (eg tartaric acid) and/or tricarboxylic acids (eg citric acid) with amines and/or alcohols. ester-imide, ester-amide, di-ester, and di-amide friction modifiers prepared by reacting in the presence of an esterification catalyst. Such friction modifiers, often derived from tartaric acid, citric acid or derivatives thereof, may be derived from branched amines and/or alcohols, such that the friction modifier itself has a significant amount of branched hydrocarbyl groups present in its structure. Examples of suitable branched alcohols used to prepare these friction modifiers include 2-ethylhexanol, isotridecanol, Guerbet alcohol, or mixtures thereof.

In different embodiments, the fuel composition may have a composition set forth in the table below:

lubricating viscosity oil

The lubricating composition comprises a lubricating viscosity oil. Such oils include natural and synthetic oils, oils derived from hydrocracking, hydrogenation and hydrogenation, unrefined, refined, re-refined oils or mixtures thereof. A more detailed description of crude, refined and re-refined oils can be found in International Publication WO2008/147704, paragraphs [0054] to [0056] (a similar disclosure is provided in US Patent Publication 2010/0197536, [0072] to [ 0073). A more detailed description of natural and synthetic lubricating oils is described in paragraphs [0058] to [0059] of WO2008/147704, respectively (a similar disclosure is provided in US Patent Publication 2010/0197536, see [0075] to [0076]). Synthetic oils may also be prepared by Fischer-Tropsch reactions and may typically be hydroisomerized Fischer-Tropsch hydrocarbons or waxes. In one embodiment, the oil may be prepared by a Fischer-Tropsch gas-to-liquid synthesis procedure as well as other gas-to-liquid oils.

Lubricating viscosity oils may also be defined as specified in the April 2008 version of "Appendix E - API Base Oil Interchangeability Guidelines for Passenger Car Motor Oils and Diesel Engine Oils", Section 1.3 Sub-Heading 1.3 "Base Stock Categories". there is. API guidance is also summarized in US Pat. No. 7,285,516 (see column 11, line 64 to column 12, line 10). In one embodiment, the lubricating viscosity oil may be an API Group II, Group III or Group IV oil, or a mixture thereof. The five base oil groups are:

The amount of oil of lubricating viscosity present is typically the remainder after subtracting the sum of the amounts of the compound of the present invention and other performance additives from 100 wt % (wt %).

Lubricating compositions may be in the form of concentrates and/or fully formulated lubricants. When the lubricating composition of the present invention (including the additives disclosed herein) is in the form of a concentrate that can be combined with additional oils to form, in whole or in part, a finished lubricant, such additives to lubricating viscosity oils and/or The ratio of diluent oil includes in the range of 1:99 to 99:1 by weight, or 80:20 to 10:90 by weight.

In one embodiment, the base oil has a kinematic viscosity at 100° C. of 2 mm ² /s (centistokes - cSt) to 16 mm ² /s, 3 mm ² /s to 10 mm ² /s, or even 4 mm ² /s to 8 mm ² /s. have

The ability of a base oil to act as a solvent (ie, solvent power) may be a contributing factor in increasing the frequency of LSPI events during operation of a fuel-direct injection engine. Base oil dissolving power can be measured as the ability of an unadded base oil to act as a solvent for the polar component. In general, base oil dissolving power decreases as the base oil group moves from group I to group IV (PAO). That is, the dissolving power of the base oil can be ranked as follows for the oils of the corresponding dynamic viscosity: Group I > Group II > Group III > Group IV. Base oil dissolving power also decreases with increasing viscosity within a base oil group; Base oils of lower viscosity tend to exhibit better dissolving power than similar base oils of higher viscosity. Base oil solubility can be measured in aniline points (ASTM D611).

In one embodiment, the base oil comprises at least 30 wt % of a Group II or Group III base oil. In another embodiment, the base oil comprises at least 60 wt % of a Group II or Group III base oil, or at least 80 wt % of a Group II or Group III base oil. In one embodiment, the lubricant composition comprises less than 20 wt % of a Group IV (ie, polyalphaolefin) base oil. In another embodiment, the base oil comprises less than 10 wt % of a Group IV base oil. In one embodiment, the lubricating composition is substantially free of Group IV base oils (ie, contains less than 0.5 wt %).

Ester base fluids characterized as Group V oils have high levels of dissolving power as a result of their polarity. The addition of esters at low levels (typically less than 10 wt %) to the lubricating composition can significantly increase the resulting dissolving power of the base oil mixture. Esters can be grouped into two broad categories: synthetic and natural. The ester base fluid will have a kinematic viscosity suitable for use in engine oil lubricants at 100° C., such as from 2 cSt to 30 cSt, or from 3 cSt to 20 cSt or even from 4 cSt to 12 cSt.

Synthetic esters include dicarboxylic acids (e.g., esters) with any of a variety of monohydric alcohols (e.g., butyl alcohol, hexyl alcohol, dodecyl alcohol, 2-ethylhexyl alcohol, ethylene glycol, diethylene glycol monoether, and propylene glycol). For example, phthalic acid, succinic acid, alkyl succinic acid and alkenyl succinic acid, maleic acid, azelaic acid, suberic acid, sebacic acid, fumaric acid, adipic acid, linoleic acid dimer, malonic acid, alkyl malonic acid, and alkenyl esters of malonic acid). Specific examples of these esters include dibutyl adipate, di(2-ethylhexyl)sebacate, di-n-hexyl fumarate, dioctyl sebacate, diisooctyl azelate, diisodecyl azelate, dioctyl phthalate, didecyl phthalate, dieicosyl sebacate, 2-ethylhexyl diester of linoleic acid dimer, and complex ester formed by reacting 1 mole of sebacic acid with 2 moles of tetraethylene glycol and 2 moles of 2-ethylhexanoic acid do. Other synthetic esters include those prepared from C5 to C12 monocarboxylic acids and polyols and polyol ethers such as neopentyl glycol, trimethylolpropane, pentaerythritol, dipentaerythritol and tripentaerythritol. The ester may also be a monoester of a mono-carboxylic acid and a monohydric alcohol.

Natural (or bio-derived) esters refer to substances derived from renewable biological resources, organisms or entities, and are distinct from substances derived from petroleum or equivalent raw materials. Natural esters include fatty acid triglycerides, hydrolyzed or partially hydrolyzed triglycerides, or transesterified triglyceride esters such as fatty acid methyl esters (or FAMEs). Suitable triglycerides include, but are not limited to, palm oil, soybean oil, sunflower oil, rapeseed oil, olive oil, linseed oil and related substances. Other sources of triglycerides include, but are not limited to, algae, zoonotic tallow and zooplankton. Methods for producing biolubricating agents from natural triglycerides are described, for example, in US Patent Publication 2011/0009300A1.

In one embodiment, the lubricating composition comprises at least 2 wt % of the ester base fluid. In one embodiment, the lubricating composition of the present invention comprises at least 4 wt % ester base fluid, or at least 7 wt % ester base fluid, or even at least 10 wt % ester base fluid.

overbased sodium detergent

Metal overbased detergents are alternatively referred to as overbased detergents, metal-containing overbased detergents or overbased salts, depending on the stoichiometry of the substrate reacting with the metal and certain acidic organic compounds, i.e. the metal. Characterized by a metal content that exceeds the metal content required for neutralization. The overbased sodium detergent may include one or more of non-sulfur containing phenates, sulfur containing phenates, sulfonates, salicylates, and mixtures thereof.

The amount of excess metal is generally expressed in terms of substrate to metal ratio. In the prior art and herein, the term “metal ratio” refers to the hydrocarbyl substituted organic acid to be overbased; Total number of metals in overbased salts relative to chemical equivalents of metals in salts predicted to arise from the reaction of the two reactants according to the known chemical reactivity and stoichiometry of a hydrocarbyl-substituted phenol or mixture thereof with a base metal compound. Used to define the ratio of chemical equivalents. Thus, in normal or neutral salts (ie soap) the metal ratio is greater than 1, and in overbased salts the metal ratio is greater than 1, especially greater than 1.3. The overbased sodium detergent of the present invention may have a metal ratio of 5 to 30, or a metal ratio of 7 to 22, or a metal ratio of at least 11.

Sodium-containing detergents also contain phenate and/or sulfonate components, such as those described in U.S. Patent Nos. 6,429,178; 6,429,179; 6,153,565; and a "hybrid" detergent formed with a mixed surfactant system comprising phenate-salicylate, sulfonate-phenate, sulfonate-salicylate, sulfonate-phenate-salicylate as described in 6,281,179. may include For example, if a hybrid sulfonate/phenate detergent is used, the hybrid detergent would be considered equivalent to an amount of distinct phenate and sulfonate detergent incorporating similar amounts of phenate and sulfonate soap, respectively. Overbased phenates and salicylates generally have a total number of bases of 180 to 450 TBN. Overbased sulfonates generally have a total number of bases from 250 to 600, or from 300 to 500. Overbased detergents are known in the art.

Alkylphenols are often used as components and/or building blocks of overbased detergents. Alkylphenols can be used to prepare phenate, salicylate, salixarate or saligenin detergents or mixtures thereof. Suitable alkylphenols may include para-substituted hydrocarbyl phenols. A hydrocarbyl group can be a linear or branched aliphatic group of 1 to 60 carbon atoms, 8 to 40 carbon atoms, 10 to 24 carbon atoms, 12 to 20 carbon atoms, or 16 to 24 carbon atoms. In one embodiment, the alkylphenol overbased detergent is prepared from an alkylphenol or mixtures thereof that is free or substantially free (ie, containing less than 0.1% by weight) of p-dodecylphenol. In one embodiment, the lubricating composition of the present invention contains less than 0.3 weight percent alkylphenol, less than 0.1 weight percent alkylphenol, or less than 0.05 weight percent alkylphenol.

The overbased sodium detergent may be salts of phenates, sulfur-containing phenates, sulfonates, salizarates and salicylates. In one embodiment, the overbased sodium detergent may be present in an amount to deliver at least 25 ppm by weight sodium, at least 50 ppm sodium by weight, or at least 85 ppm sodium by weight to the lubricating composition. In one embodiment, the overbased sodium detergent comprises 225 weight ppm or less sodium, 200 weight ppm or less sodium, 200 weight ppm or less sodium, 185 weight ppm or less sodium, or 150 weight ppm or less sodium in the lubricating composition. It may be present in an amount to deliver.

In one embodiment, the lubricating composition comprises at least one sodium-free metal containing detergent in addition to the overbased sodium detergent of the present invention. The sodium-free overbased metal-containing detergent may be an alkali metal or alkaline earth metal salt. In one embodiment, the overbased detergent can be a calcium salt, a magnesium salt, or a mixture thereof, of a phenate, a sulfur-containing phenate, a sulfonate, a salizarate and a salicylate. In one embodiment, the sodium-free overbased detergent is a calcium detergent, a magnesium detergent, or a mixture thereof. In one embodiment, the overbased calcium detergent lubricates at least 500 ppm by weight calcium and up to 2000 ppm calcium by weight, or at least 700 ppm calcium by weight, or at least 1100 ppm calcium by weight, or up to 1700 ppm calcium by weight. It may be present in an amount to deliver to the composition. In one embodiment, the at least one sodium-free overbased detergent comprises 1200 wt ppm or less, or 800 wt ppm or less, or 600 wt ppm or less, or 200 wt ppm or less, or 45 wt ppm or less magnesium to the lubricating composition. It may be present in an amount to deliver. In one embodiment, the lubricating composition is essentially free (ie, containing less than 10 ppm) magnesium resulting from an overbased detergent. In one embodiment, the at least one sodium-free overbased detergent may be present in an amount that delivers at least 200 ppm by weight magnesium, or at least 450 ppm magnesium by weight, or at least 700 ppm magnesium by weight to the lubricating composition. . In one embodiment, both calcium and magnesium containing detergents may be present in the lubricating composition in addition to the sodium overbased detergent. Sodium, calcium and magnesium detergents have a sodium to calcium to magnesium weight ratio of 1:9:0 to 4:6:0, or 1:8:1 to 2:4:4 or 1:0:9 to 4:2: It can exist so as to be 4.

In one embodiment, the sulfonate detergent is primarily a linear alkylbenzene sulfonate having a metal ratio of at least 8 as described in paragraphs [0026] to [0037] of US Patent Publication 2005/065045 (and issued as US 7,407,919). It may be detergent. Linear alkylbenzene sulfonate detergents may be particularly useful to aid in improving fuel economy. The linear alkyl group is attached somewhere in the benzene ring along the linear chain of the alkyl group, but often at the 2, 3 or 4 position of the linear chain and in some cases, mainly at the 2 position, resulting in a linear alkylbenzene sulfonate detergent. can

Salicylate detergents and overbased salicylate detergents can be prepared in at least two different ways. Carbonylation of p-alkylphenols (also referred to as carboxylation) is described in a number of publications, including US Pat. No. 8,399,388. Carbonylation may be followed by overbased to form an overbased salicylate detergent. Suitable p-alkylphenols include those having linear and/or branched hydrocarbyl groups of 1 to 60 carbon atoms. Salicylate detergents can also be prepared by alkylation of salicylic acid followed by overbase as described in US Pat. No. 7,009,072. Salicylate detergents prepared in this way are prepared from linear and/or branched alkylating agents (typically 1-olefins) containing from 6 to 50 carbon atoms, from 10 to 30 carbon atoms, or from 14 to 24 carbon atoms. can be In one embodiment, the overbased detergent of the present invention is a salicylate detergent. In one embodiment, the salicylate detergents of the present invention are free of unreacted p-alkylphenol (ie, contain less than 0.1% by weight). In one embodiment, the salicylate detergents of the present invention are prepared by alkylation of salicylic acid.

The metal-containing overbased detergent may be present at 0.2 wt % to 15 wt %, or 0.3 wt % to 10 wt %, or 0.3 wt % to 8 wt %, or 0.4 wt % to 3 wt %. For example, in heavy duty diesel engines, the detergent may be present at 2 wt % to 3 wt % of the lubricating composition. In passenger car engines, the detergent may be present in 0.2 wt % to 1 wt % of the lubricating composition.

The metal-containing detergent provides ash sulfate to the lubricating composition. Ash sulfate can be measured by ASTM D874. In one embodiment, the lubricating composition of the present invention comprises a metal-containing detergent in an amount to deliver at least 0.4% by weight sulfate ash to the total composition. In another embodiment, the metal-containing detergent is present in an amount to deliver to the lubricating composition at least 0.6% by weight ash sulfate, or at least 0.75% ash sulfate, or even at least 0.9% ash sulfate. In one embodiment, the metal-containing overbased detergent is present in an amount to deliver 0.1 wt% to 0.8 wt% sulfuric ash to the lubricating composition.

In addition to ash and TBN, overbased detergents provide detergent soaps, also called neutral detergent salts, to lubricating compositions. Soaps, which are metal salts of the substrate, can act as surfactants in the lubricating composition. In one embodiment, the lubricating composition comprises from 0.05% to 1.5% by weight of detergent soap, or from 0.1% to 0.9% by weight of detergent soap. In one embodiment, the lubricating composition contains no more than 0.5% by weight of detergent soap. The overbased detergent may have an ash:soap weight ratio of 5:1 to 1:2.3, alternatively 3.5:1 to 1:2, or 2.9:1 to 1:1:7.

Other performance additives

The compositions of the present invention may optionally include one or more additional performance additives. Such additional performance additives may include one or more metal deactivators, viscosity modifiers, antioxidants, friction modifiers, abrasion resistance agents, corrosion inhibitors, dispersants, dispersants viscosity modifiers, extreme pressure agents, antioxidants (other than those of the present invention), foam inhibitors, demulsifiers, pour point depressants, seal swelling agents, and any combination or mixture thereof. Typically, a fully formulated lubricating oil will contain one or more of these performance additives and often a package of multiple performance additives.

In one embodiment, the present invention provides a lubricating composition further comprising a dispersant, an anti-wear agent, a dispersant viscosity modifier, a friction modifier, a viscosity modifier, an antioxidant, a detergent (different from that of the present invention), or a combination thereof, , each of the additives listed herein may be a mixture of two or more of those types of additives. In one embodiment, the present invention provides polyisobutylene succinimide dispersants, anti-wear agents, dispersants, viscosity modifiers, friction modifiers, viscosity modifiers (typically olefin copolymers such as ethylene-propylene copolymers), antioxidants (phenols and amines) Provided is a lubricating composition further comprising an antioxidant), an overbased detergent (including an overbased sulfonate and a phenate), or a combination thereof, each of the additives listed herein being 2 of an additive of its type. It may be a mixture of two or more.

In one embodiment, the present invention provides a lubricating composition further comprising an ashless antioxidant. The ashless antioxidant may include one or more of an arylamine, a diarylamine, an alkylated arylamine, an alkylated diaryl amine, a phenol, a hindered phenol, a sulfurized olefin, or mixtures thereof. In one embodiment, the lubricating composition comprises an antioxidant or a mixture thereof. The antioxidant is present in an amount of 0 wt% to 15 wt%, alternatively 0.1 wt% to 10 wt%, alternatively 0.5 wt% to 5 wt%, alternatively 0.5 wt% to 3 wt%, alternatively 0.3 wt% to 1.5 wt% of the lubricating composition. may exist.

The diarylamine or alkylated diarylamine may be phenyl-α-naphthylamine (PANA), an alkylated diphenylamine, or an alkylated phenylnaphthylamine, or mixtures thereof. Alkylated diphenylamines include di-nonylated diphenylamine, nonyl diphenylamine, octyl diphenylamine, di-octylated diphenylamine, di-decylated diphenylamine, decyl diphenylamine and their mixtures may be included. In one embodiment, the diphenylamine may include nonyl diphenylamine, dinonyl diphenylamine, octyl diphenylamine, dioctyl diphenylamine, or mixtures thereof. In one embodiment, the alkylated diphenylamine can include nonyl diphenylamine, or dinonyl diphenylamine. The alkylated diarylamine may include octyl, di-octyl, nonyl, di-nonyl, decyl or di-decyl phenylnaphthylamine.

The diarylamine antioxidants of the present invention may be present from 0.1% to 10%, from 0.35% to 5% or even from 0.5% to 2% by weight of such lubricating composition.

The phenolic antioxidant may be a simple alkyl phenol, a hindered phenol or a coupled phenolic compound.

Hindered phenolic antioxidants often contain secondary butyl and/or tertiary butyl groups as sterically hindered groups. The phenol group may be further substituted with a hydrocarbyl group (typically a linear or branched alkyl) and/or a bridging group connected to a second aromatic group. Examples of suitable hindered phenolic antioxidants are 2,6-di-tert-butylphenol, 4-methyl-2,6-di-tert-butylphenol, 4-ethyl-2,6-di-tert- Butylphenol, 4-propyl-2,6-di-tert-butylphenol or 4-butyl-2,6-di-tert-butylphenol, 4-dodecyl-2,6-di-tert-butyl phenol, or butyl 3-(3,5-ditert-butyl-4-hydroxyphenyl)propanoate. In one embodiment, the hindered phenolic antioxidant may be an ester, including, for example, Irganox ^™ L-135 from Ciba.

Coupled phenols often contain two alkylphenols coupled with an alkylene group to form a bisphenol compound. Examples of suitable coupled phenolic compounds include 4,4'-methylene bis-(2,6-di-tert-butyl phenol), 4-methyl-2,6-di-tert-butylphenol, 2,2 '-bis-(6-t-butyl-4-heptylphenol); 4,4'-bis(2,6-di-t-butyl phenol), 2,2'-methylenebis(4-methyl-6-t-butylphenol) and 2,2'-methylene bis(4-ethyl -6-t-butylphenol).

The phenols of the present invention also include polyvalent aromatic compounds and derivatives thereof. Examples of suitable polyvalent aromatic compounds include gallic acid, 2,5-dihydroxybenzoic acid, 2,6-dihydroxybenzoic acid, 1,4-dihydroxy-2-naphthoic acid, 3,5-dihydroxynaphthoic acid, esters and amides of 3,7-dihydroxy naphthoic acid, and mixtures thereof.

In one embodiment, the phenolic antioxidant comprises a hindered phenol. In another embodiment, the hindered phenol is derived from 2,6-ditertbutyl phenol.

In one embodiment, the lubricating composition of the present invention ranges from 0.01 wt% to 5 wt%, or from 0.1 wt% to 4 wt%, or from 0.2 wt% to 3 wt%, or from 0.5 wt% to 2 wt% of the lubricating composition. of phenolic antioxidants.

Sulfurized olefins are well known commercial materials, and those that are substantially free of nitrogen, i.e., free of nitrogen functionality are readily available. Olefin-based compounds that can be sulfided exist in a variety of nature. They contain at least one olefinic double bond, which is defined as a non-aromatic double bond; That is, it contains a bond connecting two aliphatic carbon atoms. These materials generally have sulfide bonds having 1 to 10, for example 1 to 4, or 1 or 2 sulfur atoms.

The ashless antioxidants may be used separately or in combination. In one embodiment of the present invention, two or more different antioxidants are used in combination such that each of the at least two antioxidants is present in at least 0.1% by weight, wherein the combined amount of ashless antioxidants is 0.5 to 5% by weight. In one embodiment, each ashless antioxidant may be present in at least 0.25 to 3 weight percent.

In one embodiment, the present invention provides a lubricating composition further comprising a molybdenum compound. The molybdenum compound may be selected from the group consisting of molybdenum dialkyldithiophosphates, molybdenum dithiocarbamates, amine salts of molybdenum compounds, and mixtures thereof. The molybdenum compound may provide 0 to 1000 ppm, or 5 to 1000 ppm, or 10 to 750 ppm, or 5 ppm to 300 ppm, or 20 ppm to 250 ppm of molybdenum to the lubricating composition.

Suitable dispersants for use in the compositions of the present invention include succinimide dispersants. In one embodiment, the dispersant may be present as a single dispersant. In one embodiment, the dispersant may be present as a mixture of two or three different dispersants, wherein at least one may be a succinimide dispersant.

The succinimide dispersant may be a derivative of an aliphatic polyamine or a mixture thereof. The aliphatic polyamine may be an aliphatic polyamine such as ethylenepolyamine, propylenepolyamine, butylenepolyamine, or mixtures thereof. In one embodiment, the aliphatic polyamine may be ethylenepolyamine. In one embodiment, the aliphatic polyamine is selected from the group consisting of ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, polyamine still bottoms, and mixtures thereof. can be

The dispersant may be an N-substituted long chain alkenyl succinimide. Examples of N-substituted long chain alkenyl succinimides include polyisobutylene succinimides. Typically the polyisobutylene from which polyisobutylene succinic anhydride is derived has a number average molecular weight of 350 to 5000, or 550 to 3000 or 750 to 2500. Succinimide dispersants and their preparation are described, for example, in US Pat. and EP Patent 0 355 895B1.

The dispersant may also be post-treated by conventional methods by reaction with any of a variety of agents. Among these are boron compounds, urea, thiourea, dimercaptothiadiazole, carbon disulfide, aldehyde, ketone, carboxylic acid, hydrocarbon-substituted succinic anhydride, maleic anhydride, nitrile, epoxide and phosphorus compound.

The dispersant may be present in 0.01 wt % to 20 wt %, or 0.1 wt % to 15 wt %, or 0.1 wt % to 10 wt %, or 1 wt % to 6 wt % of the lubricating composition.

In one embodiment, the lubricating composition of the present invention further comprises a dispersant viscosity modifier. The dispersant viscosity modifier may be present in 0 wt % to 5 wt %, or 0 wt % to 4 wt %, or 0.05 wt % to 2 wt % of the lubricating composition.

Suitable dispersant viscosity modifiers include functionalized polyolefins, for example, ethylene-propylene copolymers functionalized with maleic anhydride and acylating agents such as amines; polymethacrylates functionalized with amines, or esterified styrene-maleic anhydride copolymers reacted with amines. A more detailed description of dispersant viscosity modifiers can be found in International Publication Nos. WO2006/015130 or US Pat. No. 4,863,623; 6,107,257; 6,107,258; and 6,117,825. In one embodiment, the dispersant viscosity modifier is disclosed in U.S. Patent 4,863,623 (see column 2, line 15 to column 3, line 52) or International Publication WO2006/015130 (see page 2, paragraph [0008], preparation examples are described in paragraphs [0065] to [0073] ]).

In one embodiment, the present invention provides a lubricating composition further comprising a phosphorus-containing anti-wear agent. Typically, the phosphorus-containing abrasion resistant agent may be a zinc dialkyldithiophosphate. Zinc dialkyldithiophosphates are known in the art. The anti-wear agent may be present in 0 wt % to 3 wt %, or 0.1 wt % to 1.5 wt %, or 0.5 wt % to 0.9 wt % of the lubricating composition.

In one embodiment, the present invention provides a lubricating composition further comprising a friction modifier. Examples of friction modifiers include long-chain fatty acid derivatives, fatty esters, or epoxides of amines; fatty imidazolines such as condensation products of carboxylic acids with polyalkylene-polyamines; amine salts of alkylphosphoric acids; fatty alkyl tartrates; fatty alkyl tartrimides; or fatty alkyl tartramides. The term fat as used herein may mean having a C8-22 linear alkyl group.

Friction modifiers may also include substances such as sulfurized fatty compounds and olefins, molybdenum dialkyldithiophosphates, molybdenum dithiocarbamates, sunflower oil or monoesters of polyols and aliphatic carboxylic acids.

In one embodiment, the friction modifier is a long chain fatty acid derivative of an amine, a long chain fatty ester, or a long chain fatty epoxide; fatty imidazolines; amine salts of alkylphosphoric acids; fatty alkyl tartrates; fatty alkyl tartrimides; and fatty alkyl tartramides. The friction modifier may be present in 0 wt % to 6 wt %, or 0.05 wt % to 4 wt %, or 0.1 wt % to 2 wt % of the lubricating composition.

In one embodiment, the friction modifier may be a long chain fatty acid ester. In another embodiment, the long chain fatty acid ester can be a mono-ester or diester or mixtures thereof, and in another embodiment, the long chain fatty acid ester can be a triglyceride.

Other performance additives, such as corrosion inhibitors, are those described in paragraphs 5 to 8 of US application US05/038319 published as WO2006/047486, octyl octanamide, dodecenyl succinic acid or anhydride, and condensation of fatty acids such as oleic acid with polyamines. includes products. In one embodiment, the corrosion inhibitor comprises Synalox® (a registered trademark of The Dow Chemical Company) corrosion inhibitor. Synalox® corrosion inhibitors can be homopolymers or copolymers of propylene oxide. Synalox® corrosion inhibitor is further described in the product brochure under Published Form No. 118-01453-0702 AMS from The Dow Chemical Company. The product brochure is titled "SYNALOX Lubricants, High-Performance Polyglycols for Demanding Applications."

The lubricating composition may be a derivative of benzotriazole (typically tolyltriazole), a dimercaptothiadiazole derivative, 1,2,4-triazole, benzimidazole, 2-alkyldithiobenzimidazole or 2-alkyl metal deactivators including dithiobenzothiazole; foam inhibitors including copolymers of ethyl acrylate and 2-ethylhexyl acrylate and copolymers of ethyl acrylate and 2-ethylhexyl acrylate and vinyl acetate; demulsifiers including trialkyl phosphates, polyethylene glycols, polyethylene oxides, polypropylene oxides and (ethylene oxide-propylene oxide) polymers; and a pour point depressant comprising an ester of maleic anhydride-styrene, polymethacrylate, polyacrylate or polyacrylamide.

Pour point depressants that may be useful in the compositions of the present invention further include polyalphaolefins, esters of maleic anhydride-styrene, poly(meth)acrylates, polyacrylates or polyacrylamides.

In another embodiment, the lubricating composition may have a composition set forth in the table below:

The present invention provides the surprising ability to prevent damage to the engine during operation due to a pre-ignition event resulting from direct injection of gasoline into the combustion chamber. This is achieved while maintaining fuel economy performance, low sulfate ash levels, improved sediment control and other limitations required by increasingly stringent government regulations.

industrial application

As described above, the present invention provides a method of lubricating an internal combustion engine comprising supplying the lubricating composition disclosed herein to the internal combustion engine. Generally, a lubricant is added to the lubrication system of an internal combustion engine, which in turn delivers the lubricating composition to critical parts of the engine in need of lubrication during operation of the engine.

The lubricating compositions described above may be used in internal combustion engines. The engine component may have a surface (typically a steel surface) of steel or aluminum, and may also be coated, for example, with a diamondoid carbon (DLC) coating.

The aluminum surface may be composed of an aluminum alloy, which may be a eutectic or hyper-eutectic aluminum alloy (eg, derived from aluminum silicate, aluminum oxide or other ceramic materials). The aluminum surface may be present on a cylinder bore, cylinder block or piston ring with an aluminum alloy, or aluminum composite.

The internal combustion engine may be fitted with an exhaust gas control system or a turbocharger. Examples of exhaust gas control systems include systems using a diesel particulate filter (DPF), or selective catalytic reduction (SCR).

The internal combustion engine of the present invention is distinct from a gas turbine. In an internal combustion engine, individual combustion events convert linear reciprocating power into rotational torque via a rod and crankshaft. In contrast, in a gas turbine (which may also be referred to as a jet engine), the continuous combustion process continuously generates rotational torque without translation, and can also generate propulsion at the exhaust. These differences in operating conditions of gas turbines and internal combustion engines result in different operating environments and stresses.

Lubricant compositions for internal combustion engines can be suitable for all engine lubricants regardless of sulfur, phosphorus or ash sulfate (ASTM D-874) content. The sulfur content of the engine oil lubricant may be 1 wt % or less, or 0.8 wt % or less, or 0.5 wt % or less, or 0.3 wt % or less. In one embodiment, the sulfur content may range from 0.001 wt % to 0.5 wt %, or from 0.01 wt % to 0.3 wt %. The phosphorus content is 0.2 wt% or less, or 0.12 wt% or less, or 0.1 wt% or less, or 0.085 wt% or less, or 0.08 wt% or less, or even 0.06 wt% or less , 0.055 wt % or less, or 0.05 wt % or less. In one embodiment, the phosphorus content can be from 100 ppm to 1000 ppm, or from 200 ppm to 600 ppm. The total ash content is 2 wt% or less, or 1.5 wt% or less, or 1.1 wt% or less, or 1 wt% or less, or 0.8 wt% or less, or 0.5 wt% or less less, or 0.4 wt % or less. In one embodiment, the ash sulfate content may be from 0.05 wt% to 0.9 wt%, or from 0.1 wt% to 0.2 wt% or 0.45 wt%.

In one embodiment, the lubricating composition may be an engine oil, wherein the lubricating composition has (i) a sulfur content of 0.5 wt % or less, (ii) a phosphorus content of 0.1 wt % or less, or (iii) 1.5 wt % or less ash sulfate, or a combination thereof.

Example

The invention will be further illustrated by the following examples, which present particularly advantageous embodiments. While the examples are provided to illustrate the invention, they are not intended to limit the invention.

lubricating composition

Conventional additives including polymeric viscosity modifiers, ashless succinimide dispersants, overbased detergents, antioxidants (combinations of phenolic acid esters and diarylamines), zinc dialkyldithiophosphate (ZDDP), as well as the aforementioned additives prepared a series of 5W-20 engine lubricants of Group II lubricating viscosity base oil, of course containing other performance additives as follows (Table 1). In addition, the phosphorus, sulfur and ash contents of each example are presented partially in the table to show that each example has similar amounts of these materials, thus providing an appropriate comparison between the comparative examples and the inventive examples.

Table 1 - Lubricant composition formulation ^One

1 - All quantities given above are unless otherwise indicated. is the weight % oil- free is the standard

2 - Ca sulfonate 1: Oil free overbased calcium sulfonate TBN 520; metal ratio 10

3 - Ca sulfonate 2: Oil free overbased calcium sulfonate TBN 690; metal ratio 18

4 - Ca sulfonate 3: Oil free overbased calcium sulfonate TBN 160; Metal Ratio 2.8

5 - Ca phenate : oil free "Neutral" Calcium phenate TBN 200; Metal ratio 1.2

6 - Na sulfonate : oil free overbased Na sulfonate TBN 650

7 - Mg sulfonate : oil free overbased Mg sulfonate TBN 600

8 - alkylated diarylamine and disabled phenolic antioxidants combination

9 - dispersant: 2000 Mn from PIB manufactured PIB succinimide

10 - in the example Additional additives used include friction modifiers, pour point depressants, defoamers, corrosion inhibitors, and some amounts of diluent oils.

Table 2 - Lubricant composition formulation ( 5W-30)

1 - All quantities given above are unless otherwise indicated. is the weight % oil- free is the standard

2 - Ca Sulfonate is TBN at least 300 and metal ratio is at least 10 or more overbased Calcium Alkylbenzene is sulfonic acid .

3 - TBN ~600 people overbased magnesium sulfonate

4 - TBN Sulfur in Calcium, which is ~200 combined phenate salt

5 - ashless Antioxidants - nonylated and dinonylated diphenylamine , disabled Mixtures of phenol esters and sulfurized olefins

6 - in the example Additional additives used include friction modifiers, pour point depressants, defoamers, corrosion inhibitors, and some amounts of diluent oils.

test

Low speed pre-ignition events were measured on two engines: a Ford 2.0L Ecoboost engine and a GM 2.0L Ecotec. Both of these engines are turbocharged gasoline direct injection (GDI) engines. The Ford Ecoboost engine operates in two stages. In the first stage, the engine is run at 1500 rpm and 14.4 bar Brake Mean Effective Pressure (BMEP). During the second stage, the engine is run at 1750 rpm and 17.0 bar BMEP. The engine was run for 25,000 combustion cycles at each stage and LSPI events were counted.

The GM Ecotec engine was operated at 2,000 rpm and 22.0 bar BMEP at an oil sump temperature of 100°C. The test consists of 9 phases of 15,000 combustion cycles, each phase separated by an idle period. Thus, combustion events were counted over 135,000 combustion cycles.

LSPI events were measured by monitoring the peak cylinder pressure (PP) and mass burn fraction (MFB) of the fuel charge in the cylinder. If both criteria were met, an LSPI event was determined to have occurred. The threshold for peak cylinder pressure is generally between 9,000 and 10,000 kPa. The threshold for MFB is typically a value that causes at least 2% of the fuel charge to burn late, i.e. 5.5 degrees After Top Dead Center (ATDC). LSPI events may be reported as events per 100,000 combustion cycles, events per cycle, and/or combustion cycles per event.

Table 4 - GM Ecotec LSPI test

The data indicate that LSPI events decrease when the total detergent ash is reduced to less than 1% by weight. Partial replacement of calcium detergent with sodium detergent and optionally magnesium detergent also provided observations of reduced LSPI events. In addition, partial replacement of sulfonate detergents with phenate-based detergents induced a decrease in observable LSPI events.

It is known that some of the substances described above may interact in the final formulation, so that the ingredients of the final formulation may differ from those initially added. The products thus formed (including those formed when the lubricant composition of the present invention is used in its intended use) may not be readily delineated. Nevertheless, all such modifications and reaction products are included within the scope of this invention; The present invention includes a lubricant composition prepared by mixing the ingredients described above.

Each of the documents mentioned above is incorporated herein by reference as well as priority documents and, if any, all related applications from which this application claims benefit. Except in the examples, or where expressly indicated otherwise, all numerical quantities herein specifying materials, reaction conditions, molecular weights, number of carbon atoms, and the like, are varied by the word “about”. should be understood as Unless otherwise specified, each chemical substance or composition recited herein is to be interpreted as a commercial grade material, which may contain isomers, by-products, derivatives and other such materials generally understood to exist in commercial grade. However, unless otherwise specified, the amounts of each chemical component are presented excluding any solvents or diluent oils that may ordinarily be present in commercial materials. It should be understood that the upper and lower limits, ranges, and ratio limits set forth herein may be independently combined. Similarly, ranges and amounts for each element of the invention may be used in conjunction with ranges or amounts for any other element.

As used herein, the term "hydrocarbyl substituent" or "hydrocarbyl group" is used in its ordinary meaning well known to those skilled in the art. In particular, it refers to groups attached directly to the remainder of the molecule, having carbon atoms, and having predominantly hydrocarbon properties. Examples of hydrocarbyl groups include i) hydrocarbon substituents, i.e. aliphatic (eg alkyl or alkenyl), cycloaliphatic (eg cycloalkyl, cycloalkenyl) substituents, and aromatic-, aliphatic- and cycloaliphatic -substituted aromatic substituents as well as cyclic substituents, wherein the ring is completed through another part of the molecule (eg, two substituents together form a ring); (ii) substituted hydrocarbon substituents, i.e., in the context of the present invention, non-hydrocarbon groups that do not alter the primary hydrocarbon properties of the substituents (e.g. halo (especially chloro and fluoro), hydroxy, alkoxy, mercapto , alkylmercapto, nitro, nitroso, and sulfoxy); (iii) heterosubstituents, i.e., substituents containing other than carbon in a ring or chain composed of carbon atoms in the context of the present invention, while having the main hydrocarbon character.

Heteroatoms include sulfur, oxygen, nitrogen and include substituents such as pyridyl, furyl, thienyl and imidazolyl. In general, there will be no more than 2, preferably no more than 1 non-hydrocarbon substituent for every 10 carbon atoms in the hydrocarbyl group; Typically, there will be no non-hydrocarbon substituents on the hydrocarbyl group.

While the present invention has been described in terms of preferred embodiments thereof, it is to be understood that various modifications will become apparent to those skilled in the art upon reading this specification. Accordingly, it is to be understood that the invention disclosed herein is intended to cover such modifications as fall within the scope of the appended claims.

Claims (18)

A method of reducing low speed pre-ignition events in a spark-ignited direct injection internal combustion engine comprising supplying a lubricant composition to the engine, wherein the lubricant composition comprises 0.255% to 0.484% calcium and sodium, or calcium and magnesium an overbased calcium detergent and an overbased sodium detergent, or an overbased detergent combination comprising an overbased calcium detergent and an overbased magnesium detergent, and a lubricating viscosity base oil in an amount to deliver of lubricating viscosity),
wherein the lubricant composition further comprises a phosphorus-containing antiwear agent in an amount to deliver from 0.03% to 0.076% by weight phosphorus to the lubricant composition. The method of claim 1 , wherein the engine is operated under a load having a brake mean effective pressure (BMEP) of 10 bar or greater. The method of claim 1 , wherein the engine is operated at a speed of 3,000 rpm or less. The method of claim 1 , wherein the engine is fueled with a liquid hydrocarbon fuel, a liquid non-hydrocarbon fuel, or a mixture thereof. 5. The method of claim 4, wherein the engine is fueled by natural gas, liquefied petroleum gas (LPG), compressed natural gas (CNG) or mixtures thereof. The method of claim 1 , wherein the overbased sodium detergent comprises one or more of a sulfonate detergent, a phenate detergent, and a salicylate detergent. The method of claim 1 , wherein the lubricant composition further comprises at least one other additive selected from an ashless dispersant, an ashless antioxidant, a friction modifier, and a polymeric viscosity modifier. 7. The method of claim 6, wherein the overbased sodium detergent comprises a sulfonate detergent. 7. The method of claim 6, wherein the overbased sodium detergent comprises a salicylate detergent. The method of claim 1 , wherein the overbased sodium detergent has a metal ratio between 5 and 30. delete delete 4. The method of claim 3, wherein the lubricating composition further comprises a polyalkenyl succinimide dispersant in an amount of 0.5 to 4% by weight of the composition. The method of claim 1 , wherein the lubricating composition comprises at least 50% by weight of a Group II base oil, a Group III base oil, or a mixture thereof. The method of claim 1 , wherein the overbased sodium detergent comprises a sulfur-coupled phenate detergent. delete 16. The method of any one of claims 1-10, and 13-15, wherein the number of LSPI events is reduced by at least 10%. The method of claim 1 , wherein the low rate pre-ignition event is reduced to less than 20 LSPI events per 100,000 burn events.