Detergent-free and low-ash lubricating composition

Abstract

This disclosure describes detergent-free, low-ash lubricating compositions that achieve piston cleanliness using one or more succinimide dispersants, one or more ashless antiwear additives, and one or more antioxidants when selected ratios of sulfur, phosphorus, and nitrogen are maintained.

Description

[Technical Field]

[0001] (CROSS-REFERENCE TO RELATED APPLICATIONS) This application claims priority to U.S. Patent Application No. 18 / 068,795, filed December 20, 2022, which is incorporated herein by reference in its entirety.

[0002] FIELD OF THE INVENTION The present disclosure relates to a detergent-free, low-ash additive system and lubricating compositions including the additive system that are configured to improve piston cleanliness. [Background technology]

[0003] Automobile manufacturers continue to strive for improved efficiency and fuel economy, thereby increasing demand for engines, lubricants, and their components. This ongoing drive for improved fuel economy has, in some instances, shifted the automotive market to direct-injection gasoline (DIG) engines. However, one of the drawbacks of DIG technology is the potential for increased exhaust particulates, particularly increased levels of soot and / or ash. One option for mitigating increased soot and / or ash is the use of gasoline particulate filters (GPFs) to remove such particulates from the exhaust, but such use is not without trade-offs. While dirty GPFs can, in some circumstances, be regenerated by burning off collected soot particles, GPFs generally cannot sweep away collected levels of ash, which tend to result from small amounts of engine oil being burned off in the combustion chamber, and therefore, GPFs may have a limited lifespan. Alternatively, there is often a desire to simply reduce the level of soot and / or ash contribution from a lubricant, but reducing these contributors and still meeting the increasing demands of manufacturer and industry performance standards tends to be difficult. Lower ash-contributing components in a lubricant can be desirable, but often reducing ash-contributing components (such as detergent and / or anti-wear additives) tends to reduce other performance characteristics of the lubricant.

[0004] The ash-containing components in engine oils are typically specified by sulfated ash (SASH) limits. Engine oils often have a maximum SASH limit of 1 weight percent. However, formulating engine oils to meet lower SASH limits, such as below 0.2 weight percent, is often difficult due to the reduced performance of the oil when some of the major ash-contributing species are removed from the engine oil. In particular, calcium, magnesium, sodium, and / or lithium are examples of major ash-contributing metals typically provided in detergent additives used in engine oils. Detergent additives are generally included in engine oils for their ability to clean metal surfaces, such as pistons. Detergents are thought to function by acting as surfactants capable of removing deposits from metal surfaces; however, for this function to occur, detergents generally need to be metal salts, and therefore also contribute a certain level of ash to the lubricant to perform their intended function. Therefore, limiting these major ash contributors in engine oils to achieve lower SASH targets also tends to limit the ability of low ash engine oils to achieve acceptable levels of piston cleanliness. Summary of the Invention

[0005] In one approach or embodiment, a detergent-free, low-ash lubricating composition (as components are defined herein) that provides good piston cleanliness is described. In one aspect, the composition includes one or more base oils of lubricating viscosity, a total sulfated ash (SASH) content of less than about 0.2 weight percent as measured by ASTM D874, one or more succinimide dispersants derived from polyisobutylene having a number average molecular weight of at least about 1000, the succinimide dispersants each having a maximum of about 2 weight percent nitrogen, and at least one of the succinimide dispersants being post-treated with a boron compound, one or more ashless antiwear additives, and one or more antioxidants. In another embodiment, the composition also has a total base number (TBN) of at least about 4, at least about 1000 ppm nitrogen, no more than 100 ppm boron, no more than 800 ppm sulfur, a sulfur-to-phosphorus ratio of no more than 2.0, and a nitrogen-to-TBN ratio of no less than about 150, per ASTM D2896, and the detergent-free, low-ash lubricating composition is substantially free of calcium, barium, copper, lead, lithium, magnesium, sodium, molybdenum, zinc, and potassium. In yet another embodiment, substantially free, in the context of this disclosure, means that the detergent-free, low-ash lubricating compositions herein further have less than about 10 ppm of each of calcium, barium, copper, lead, lithium, magnesium, sodium, molybdenum, zinc, and potassium.

[0006] In still other embodiments, the composition of the preceding paragraph may have any combination of other features or embodiments. These other features or embodiments may include further comprising one or more of the following: about 500 ppm or less of phosphorus and about 600 ppm or less of sulfur; and / or the composition comprises at least about 6 times more of one or more antioxidants than the one or more ashless antiwear additives; and / or the total sulfated ash (SASH) as measured in accordance with ASTM D874 is less than about 0.1 weight percent; and / or the one or more ashless antiwear additives comprise one or more ashless dialkyldithiophosphate antiwear additives; and / or the one or more ashless dialkyldithiophosphate antiwear additives have the structure of Formula I or a salt thereof:

[0007] [ka] wherein R4 and R5 are independently a C3-C8 straight or branched alkyl group and R6 is -H or -CH3; and / or the one or more antioxidants comprise an amine antioxidant, a hindered phenol antioxidant, or a combination thereof; and / or the amine antioxidant is selected from the group comprising an aromatic amine, an alkylated diphenylamine, an alkyldiphenylamine, a di-alkyldiphenylamine, an octyldiphenylamine, a di-octyldiphenylamine, a phenyl-alpha-naphthylamine, an alkylated phenyl-alpha-naphthylamine, a hindered non-aromatic amine, or a combination thereof; and / or the one or more succinimide dispersants comprise (i) from about 1000 to about 2 and / or greater than 50 weight percent of the total nitrogen is provided by one or more antioxidants; and / or a dispersant olefin copolymer viscosity index improver comprising the reaction product of an acylated olefin copolymer and a polyamine, wherein the acylated olefin copolymer is an olefin copolymer having a number average molecular weight of from about 0.3 to about 0.01 per 1000 number average molecular weight units of the olefin copolymer, and wherein the viscosity index improver comprises a dispersant olefin copolymer having a number average molecular weight of from about 0.3 to about 0.01 per 1000 number average molecular weight units of the olefin copolymer, and wherein the viscosity index improver comprises a dispersant olefin copolymer viscosity index improver comprising ...and / or the lubricating composition comprises an olefin copolymer grafted with 75 carboxylic acid groups, the olefin copolymer having a number average molecular weight of about 40,000 to about 150,000, and the polyamine is an N-arylphenylenediamine; and / or the lubricating composition comprises about 1 weight percent to about 4 weight percent of a dispersant olefin copolymer viscosity index improver; and / or the total amount of nitrogen, sulfur, and phosphorus relative to the amount of boron (N+S+P) / B is about 20 to about 50; and / or the lubricating composition cleans piston deposits with a total weighted piston deposit merit rating of at least about 4 according to the Sequence IIIH Engine Test (ASTM D8111), and the lubricating composition exhibits an average engine varnish (AES) rating of at least 8 Merit and / or an average engine sludge rating of at least 7.6 Merit according to the Sequence VH Test (ASTM D8256).

[0008] In another approach or embodiment, the present disclosure also provides a method of lubricating a combustion engine using a detergent-free, low ash lubricating composition (these components are defined herein). In an aspect, the method herein comprises lubricating a combustion engine with the detergent-free, low ash lubricating composition, the detergent-free, low ash lubricating composition comprising one or more base oils of lubricating viscosity, less than about 0.2 weight percent total sulfated ash (SASH) as measured by ASTM D874, one or more succinimide dispersants derived from polyisobutylene having a number average molecular weight of at least about 1000, the succinimide dispersants each having a maximum of about 2 weight percent nitrogen, and at least one of the succinimide dispersants being post-treated with a boron compound, one or more ashless antiwear additives, one or more antioxidants, and one or more base oils of lubricating viscosity having a total sulfated ash (SASH) of less than about 0.2 weight percent as measured by ASTM D874. and a nitrogen-to-TBN ratio of at least about 150 or greater, according to ASTM D2896. The detergent-free, low-ash lubricating composition is substantially free of calcium, barium, copper, lead, lithium, magnesium, sodium, molybdenum, zinc, and potassium, and comprises a total base number (TBN) of at least about 4, at least about 1000 ppm nitrogen, no more than 100 ppm boron, no more than 800 ppm sulfur, a sulfur-to-phosphorus ratio of no more than 2.0, and a nitrogen-to-TBN ratio of at least about 150, according to ASTM D2896. In another aspect, a method of lubricating with the lubricating composition herein cleans piston deposits according to the Sequence IIIH Engine Test (ASTM D8111) with a total weighted piston deposit merit rating of at least about 4, and the lubricating composition exhibits an average engine varnish (AES) rating of at least 8 Merit and / or an average engine sludge rating of at least 7.6 Merit, according to the Sequence VH Test (ASTM D8256).

[0009] In yet other approaches or embodiments, the method described in the preceding paragraph may include any combination of other features, method steps, or embodiments. These other features, method steps, or embodiments may include one or more of the following: the composition further comprises less than about 10 ppm of each of calcium, barium, copper, lead, lithium, magnesium, sodium, molybdenum, zinc, and potassium; and / or further comprises not more than about 500 ppm of phosphorus and not more than about 600 ppm of sulfur; and / or the composition comprises at least about 6 times more antioxidants than the one or more ashless antiwear additives; and / or the total sulfated ash (SASH) as measured in accordance with ASTM D874 is less than about 0.1 weight percent; and / or the one or more ashless antiwear additives comprise one or more ashless dialkyldithiophosphate antiwear additives; and / or the one or more ashless dialkyldithiophosphate antiwear additives have the structure of Formula I or a salt thereof:

[0010] [ka] wherein R4 and R5 are independently a C3-C8 straight or branched alkyl group and R6 is -H or -CH3; and / or the one or more antioxidants comprise an amine antioxidant, a hindered phenol antioxidant, or a combination thereof; and / or the amine antioxidant is selected from the group comprising an aromatic amine, an alkylated diphenylamine, an alkyldiphenylamine, a di-alkyldiphenylamine, an octyldiphenylamine, a di-octyldiphenylamine, a phenyl-alpha-naphthylamine, an alkylated phenyl-alpha-naphthylamine, a hindered non-aromatic amine, or a combination thereof; and / or the one or more succinimide dispersants are selected from the group comprising: (i) a succinimide dispersant derived from polyisobutylene having a number average molecular weight of from about 1000 to about 2000 and post-treated with a boron compound, (ii) a succinimide dispersant derived from polyisobutylene having a number average molecular weight of greater than about 2000, and (iii) a succinimide derived from polyisobutylene having a number average molecular weight of 1000 to about 2000; and / or greater than 50 weight percent of the total nitrogen is provided by one or more antioxidants; and / or further comprises a dispersant olefin copolymer viscosity index improver comprising the reaction product of an acylated olefin copolymer and a polyamine, wherein the acylated olefin copolymer comprises an olefin copolymer having from about 0.3 to about 0.75 carboxylic acid groups grafted per 1000 number average molecular weight units of the olefin copolymer, the olefin copolymer having a number average molecular weight of from about 40,000 to about 150,000, and the polyamine is an N-arylphenylenediamine; and / or the lubricating composition comprises from about 1 weight percent to about 4 weight percent of the dispersant olefin copolymer viscosity index improver; and / or the total amount of nitrogen, sulfur, and phosphorus to the amount of boron (N+S+P) / B is from about 20 to about 50.

[0011] In yet another approach or aspect, the present disclosure describes the use of any embodiment of the detergent-free, low ash lubricating compositions of the present summary to clean piston deposits and achieve a total weighted piston deposit merit rating of at least about 4 according to the Sequence IIIH Engine Test (ASTM D8111) and / or achieve an average engine varnish (AES) rating of at least 8 Merit and / or an average engine sludge rating of at least 7.6 Merit according to the Sequence VH Test (ASTM D8256).

[0012] In the use approach described in the preceding paragraph, detergent-free and low-ash lubricating compositions (as components defined herein) include any embodiment of this Summary, and in particular comprise one or more base oils of lubricating viscosity; a total sulfated ash (SASH) of less than about 0.2 weight percent as measured by ASTM D874; one or more succinimide dispersants derived from polyisobutylene having a number average molecular weight of at least about 1000, the succinimide dispersants each having a maximum of about 2 weight percent nitrogen, and at least one of the succinimide dispersants being post-treated with a boron compound; one or more ashless antiwear additives; and one or more antioxidants. In another embodiment, the composition also comprises a total base number (TBN) of at least about 4, at least about 1000 ppm nitrogen, no more than 100 ppm boron, no more than 800 ppm sulfur, a sulfur-to-phosphorus ratio of no more than 2.0, and a nitrogen-to-TBN ratio of no less than about 150, per ASTM D2896, wherein the detergent-free, low-ash lubricating composition is substantially free of calcium, barium, copper, lead, lithium, magnesium, sodium, molybdenum, zinc, and potassium. In yet another embodiment, substantially free, in the context of use in this disclosure, means that the detergent-free, low-ash lubricating compositions herein further have less than about 10 ppm of each of calcium, barium, copper, lead, lithium, magnesium, sodium, molybdenum, zinc, and potassium.

[0013] Additional details and advantages of the present disclosure will be set forth in part in the description which follows, and / or may be learned by practice of the present disclosure. The details and advantages of the present disclosure may be realized and attained by means of the elements and combinations particularly pointed out in the appended claims. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present disclosure as claimed. DETAILED DESCRIPTION OF THE INVENTION

[0014] Sulfated ash is a measurement indicating the total weight percent of ash in a lubricating oil composition. The sulfated ash measurement of a lubricating oil composition is related to the total metal content therein and can be conveniently measured according to ASTM D874 and / or other common evaluation methods known in the art and described herein. In one aspect, the present disclosure describes low-ash additives and lubricants containing such additives that provide an extremely low sulfated ash (SASH) content of about 0.2 weight percent or less, about 0.1 weight percent or less, about 0.08 weight percent or less, about 0.06 weight percent or less, or about 0.05 weight percent or less sulfated ash content in the lubricating oil composition. In another aspect, the present disclosure also describes additives and lubricants that are free of detergent additives and therefore free of metals provided by detergents. As used herein, the detergent-free and low-ash lubricating compositions herein not only have the low SASH levels described above, but detergent-free also means that the compositions are free of detergent metals, including calcium, magnesium, sodium, and lithium. Additionally, the compositions herein are free of other ash-contributing elements: barium, copper, lead, molybdenum, zinc, and potassium. As used herein, "free" in the context of detergents and / or the mentioned metals and minerals means that the compositions herein have about 10 ppm or less, about 5 ppm or less, about 2 ppm or less, about 1 ppm or less of each element, metal, or mineral (e.g., calcium, magnesium, sodium, lithium, barium, copper, lead, molybdenum, zinc, and / or potassium) in the composition, or no detectable amounts of such elements, metals, or minerals. Despite being free of traditional detergent additives and associated metal salts from these detergents that act as surfactants, the compositions herein surprisingly achieve the desired level of piston cleanliness through careful selection of the elemental relationships of the remaining components in the composition.

[0015] More specifically, in some embodiments, the detergent-free, low ash lubricating compositions herein comprise at least one or more base oils of lubricating viscosity, less than about 0.2 weight percent total sulfated ash (SASH) as measured by ASTM D874, one or more succinimide dispersants derived from polyisobutylene having a number average molecular weight of at least about 1000, the succinimide dispersants (if more than one) each having a maximum of about 2 weight percent nitrogen, and at least one of the succinimide dispersants being post-treated with a boron compound, one or more ashless antiwear additives, one or more antioxidants, and one or more ashless antiwear additives. D2896, a total base number (TBN) of at least about 4, at least about 1000 ppm nitrogen, no more than 100 ppm boron, no more than 800 ppm sulfur, a sulfur-to-phosphorus ratio of no more than 2.0, and a nitrogen-to-TBN ratio of no less than about 150, wherein the detergent-free, low ash lubricating composition is free of calcium, barium, copper, lead, lithium, magnesium, sodium, molybdenum, zinc, and / or potassium as defined above. In another embodiment, the detergent-free, low ash lubricating composition also has a weight ratio of the total amount of nitrogen, total amount of sulfur, and total amount of phosphorus to the total amount of boron (N+S+P) / B of about 20 to about 50.

[0016] In yet other embodiments, the detergent-free, low-ash lubricating compositions herein may have limited amounts of phosphorus, sulfur, and antioxidants in certain relationships with the anti-wear additives. For example, the detergent-free, low-ash lubricating compositions herein may also have about 500 ppm or less of phosphorus, about 600 ppm or less of sulfur, and / or at least about six times more antioxidant than the one or more ashless anti-wear additives.

[0017] As shown in the examples below, such embodiments of the detergent-free, low ash lubricating compositions herein are effective in cleaning piston deposits without the use of conventional detergent additives with a total weighted piston deposit merit rating of at least about 4 when measured according to the Sequence IIIH engine test (ASTM D8111), and / or embodiments of the detergent-free, low ash lubricating compositions herein also exhibit an average engine varnish (AES) rating of at least 8 Merit and / or an average engine sludge rating of at least 7.6 Merit according to the Sequence VH test (ASTM D8256).

[0018] Ashless anti-wear additive In one approach or embodiment, the detergent-free, low-ash lubricating compositions herein include one or more ashless antiwear additives in the form of acid thiophosphates or thiophosphate esters, such as ashless, amine-free dialkyldithiophosphate acid esters or sulfur-containing phosphate esters. In an embodiment, the one or more ashless antiwear additives provide the lubricating composition with from about 100 ppm to about 500 ppm of antiwear phosphorus, in another approach, from about 150 ppm to about 450 ppm of antiwear phosphorus, in a further approach, from about 200 ppm to about 400 ppm, or in yet another approach, from about 300 ppm to about 390 ppm of antiwear phosphorus. In an alternative approach, the detergent-free, low ash lubricating compositions herein comprise from about 0.1 weight percent to about 0.5 weight percent of one or more ashless antiwear additives, in another approach from about 0.2 weight percent to about 0.48 weight percent, and in a further approach, from about 0.3 weight percent to about 0.45 weight percent of one or more ashless antiwear additives. Because the compositions herein preferably do not contain conventional ZDDP additives (i.e., in some embodiments, not more than about 10 ppm zinc from ZDDP, or no detectable amounts of ZDDP additives), the detergent-free, low ash lubricating compositions herein also preferably contain from 80 to 100 weight percent, more preferably from 90 to 100 weight percent, of the phosphorus and / or sulfur in the lubricant, and most preferably, all provided by the ashless antiwear additive.

[0019] In some embodiments, the one or more ashless antiwear additives herein are acid thiophosphates, thiophosphate esters, or sulfur-containing phosphate esters, and may have one or more sulfur-phosphorus bonds. The thiophosphate esters may be dithiophosphate esters. In a more specific approach, the acid thiophosphate or thiophosphate ester may have the structure of Formula I or a salt thereof:

[0020] [ka] wherein R4 and R5 are each independently a linear or branched C1-C10 hydrocarbyl group, and R7 is a C1-C10 linear or branched carboxyl group, or a C1-C10 linear or branched alkyl alkanoate group. Preferably, R4 and R5 are each a C3-C8 linear or branched alkyl group, and R7 is derived from 2-methylpropionic acid, so that the second phosphorus product (or a salt thereof) has the structure of Formula Ia:

[0021] [ka] wherein R4 and R5 are independently a C3 to C8 straight chain or branched alkyl group (preferably a branched C4 group), and R6 is -H or -CH3. In some approaches or embodiments, the one or more ashless antiwear additives include at least 3-[[bis(2-methylpropoxy)phosphinothioyl]thio]-2-methyl-propanoic acid.

[0022] antioxidants In another approach or embodiment, the no-detergent, low-ash lubricating compositions herein also include one or more antioxidants, preferably selected from aminic antioxidants, hindered phenolic antioxidants, or combinations thereof. As noted above, embodiments herein may include about six times more of the one or more antioxidants relative to the one or more ashless antiwear additives to achieve the desired piston cleanliness in the context of a no-detergent, low-ash lubricant.

[0023] In one approach or embodiment, the aminic antioxidant may include, but is not limited to, an antioxidant selected from aromatic amines, alkylated diphenylamines, phenyl-α-naphthylamines, alkylated phenyl-α-naphthylamines, hindered non-aromatic amines, etc., or combinations thereof. The total amount of aminic antioxidant in the detergent-free, low-ash lubricating compositions herein is an amount that delivers at least about 650 ppm of antioxidant nitrogen, in some approaches about 670 ppm to about 800 ppm of antioxidant nitrogen, in other approaches about 690 to about 750 ppm of antioxidant nitrogen, or in still further approaches about up to about 700 ppm of antioxidant nitrogen. In other approaches, the detergent-free, low-ash lubricating compositions herein may include up to about 3 weight percent aminic antioxidant, or about 1 to about 3 weight percent aminic antioxidant. In some approaches, the nitrogen from the aminic antioxidant contributes at least half of the nitrogen in the lubricant, for example, at least about 50 weight percent of the total nitrogen in a non-detergent, low-ash lubricant, and in other approaches, contributes about 50 to about 60 weight percent of the total nitrogen in a non-detergent, low-ash lubricant composition.

[0024] In some approaches, the amine antioxidant may be one or more aromatic amine antioxidants, which may include, but are not limited to, diarylamines having the formula:

[0025] [ka] wherein R' and R" each independently represent a substituted or unsubstituted aryl group having 6 to 30 carbon atoms. When substituted, suitable substituents on the aryl groups of R' and R" include an aliphatic hydrocarbon group such as an alkyl having 1 to 30 carbon atoms, a hydroxy group, a halogen radical, a carboxylic acid or ester group, or a nitro group. The aryl group can be a substituted or unsubstituted phenyl or naphthyl, particularly one in which one or both aryl groups are substituted with at least one alkyl having 4 to 30, preferably 4 to 18, and most preferably 4 to 9 carbon atoms. In some approaches, one or both aryl groups can be substituted, such as mono-alkylated diphenylamine, di-alkylated diphenylamine, C9 alkylated diphenylamines, or a mixture of mono- and di-alkylated diphenylamines.

[0026] Examples of diarylamine antioxidants that can be used include, but are not limited to, diphenylamine; various alkylated diphenylamines, 3-hydroxydiphenylamine, N-phenyl-1,2-phenylenediamine, N-phenyl-1,4-phenylenediamine, monobutyldiphenylamine, dibutyldiphenylamine, monooctyldiphenylamine, dioctyldiphenylamine, monononyldiphenylamine, dinonyldiphenylamine, monotetradecyldiphenylamine, ditetradecyldiphenylamine, phenyl-alpha-naphthylamine, monooctylphenyl-alpha-naphthylamine, phenyl-beta-naphthylamine, monoheptyldiphenylamine, diheptyl-diphenylamine, p-oriented styrenated diphenylamines, mixed butyloctyldiphenylamines, and mixed octylstyryldiphenylamines.

[0027] Suitable hindered phenol antioxidants may contain secondary butyl and / or tertiary butyl groups as steric hindrance groups. The phenol group may be further substituted with a hydrocarbyl group and / or a bridging group connecting to a second aromatic group. Examples of suitable hindered phenol antioxidants include 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, 4-butyl-2,6-di-tert-butylphenol, or 4-dodecyl-2,6-di-tert-butylphenol. In one embodiment, the hindered phenol antioxidant may be an ester and may include, for example, Irganox™ L-135 available from BASF, or an addition product derived from 2,6-di-tert-butylphenol and an alkyl acrylate, where the alkyl group may contain from about 1 to about 18, or from about 2 to about 12, or from about 2 to about 8, or from about 2 to about 6, or about 4 carbon atoms. Another commercially available hindered phenol antioxidant, which may be an ester, may include Ethanox™ 4716 available from Albemarle Corporation.

[0028] In some embodiments, the detergent-free, low-ash lubricating compositions herein may also contain from about 0.5 to about 1 weight percent of a hindered phenol antioxidant, and in other embodiments, from about 0.5 to about 0.8 weight percent of a hindered phenol antioxidant. Preferably, when the detergent-free, low-ash lubricating composition contains both an aminic antioxidant and a hindered phenol antioxidant, the composition has at least about three times more aminic antioxidant (by weight) than the hindered phenol antioxidant, and preferably from about three to about four times more aminic antioxidant (by weight) than the hindered phenol antioxidant.

[0029] one or more succinimide dispersants The detergent-free, low-ash lubricating compositions herein also include a dispersant system including one or more succinimide dispersants derived from polyisobutylene having a number average molecular weight of at least about 1000, and where two or more succinimide dispersants are included, at least one of the dispersants in the system is post-treated with a boron compound. In embodiments, less than half of the lubricant's nitrogen is provided by the dispersant, and preferably less than about 40 to 50 percent of the lubricant's nitrogen is provided by the one or more succinimide dispersants. In this approach, the succinimide dispersants provide less than about 600 to about 700 ppm of nitrogen to the lubricants herein.

[0030] In one approach, the one or more succinimide dispersants include (i) succinimide dispersants derived from polyisobutylene having a number average molecular weight of from about 1000 to less than about 2000 and that have been post-treated with a boron compound, (ii) succinimide dispersants derived from polyisobutylene having a number average molecular weight of greater than about 2000 and that have not been post-treated with boron, and (iii) succinimides derived from polyisobutylene having a number average molecular weight of from 1000 to about 2000 and that have not been post-treated with a boron compound.

[0031] Succinimide dispersants are often known as ashless dispersants because they contain no ash-forming metals before mixing into a lubricating composition and typically do not contribute any ash when added to a lubricant. Ashless dispersants are characterized by a polar group attached to a relatively high molecular weight hydrocarbon chain. Typical ashless dispersants include N-substituted long-chain alkenyl succinimides. Examples of nitrogen-substituted long-chain alkenyl succinimides include polyisobutylene succinimides having a number average molecular weight of the polyisobutylene substituent ranging from about 1,000 to about 50,000, or from about 5,000, or from about 3,000, or from about 2,000 to about 3,000, as measured by GPC. Succinimide dispersants and their preparation are disclosed, for example, in U.S. Pat. No. 7,897,696 and U.S. Pat. No. 4,234,435, both of which are incorporated herein by reference. The alkenyl substituent may be prepared from polymerizable monomers containing from about 2 to about 16, or from about 2 to about 8, or from about 2 to about 6 carbon atoms. Succinimide dispersants are typically imides formed from polyamines, typically poly(ethyleneamines).

[0032] In some approaches, preferred amines for dispersants can be selected from polyamines and hydroxylamines. Examples of polyamines that can be used include, but are not limited to, diethylenetriamine (DETA), triethylenetetramine (TETA), tetraethylenepentamine (TEPA), and higher homologues such as pentaethylamine hexamine (PEHA). In some approaches, so-called heavy polyamines can be used, which are mixtures of polyalkylene-polyamines containing small amounts of lower polyamine oligomers such as TEPA and PEHA (pentaethylenehexamine), but primarily oligomers with six or more nitrogen atoms, two or more primary amines per molecule, and more extensive branching than conventional polyamine mixtures. Heavy polyamines preferably include polyamine oligomers containing seven or more nitrogen atoms per molecule and two or more primary amines per molecule.

[0033] In some embodiments, when included in the dispersants herein, polyisobutylene (PIB) is a preferred reactant for forming the dispersant and may have a terminal double bond content of greater than 50 mol%, greater than 60 mol%, greater than 70 mol%, greater than 80 mol%, or greater than 90 mol%. Such PIB is also referred to as highly reactive PIB ("HR-PIB"). HR-PIB having a number average molecular weight in the range of about 800 to about 5000, as determined by GPC, is suitable for use in embodiments of the present disclosure. Conventional PIB typically has a terminal double bond content of less than 50 mol%, less than 40 mol%, less than 30 mol%, less than 20 mol%, or less than 10 mol%.

[0034] HR-PIB having a number-average molecular weight of about 1,000 to about 3,000, or preferably about 1,200 to about 3,000, as determined by GPC, or within the ranges stated above, may be suitable. Such HR-PIB is commercially available or can be synthesized by polymerization of isobutene in the presence of a non-chlorinated catalyst, such as boron trifluoride, as described in U.S. Pat. Nos. 4,152,499 and / or 5,739,355. When used in the aforementioned thermal ene reaction, HR-PIB can result in higher conversion rates and less precipitate formation in the reaction due to its increased reactivity. A suitable method is described in U.S. Pat. No. 7,897,696. In one embodiment, the present disclosure further includes at least one dispersant derived from polyisobutylene succinic anhydride ("PIBSA"). The PIBSA can have an average of about 1.0 to about 2.0 succinic acid moieties per polymer.

[0035] In some approaches, some of the dispersants in the detergent-free, low-ash lubricating compositions herein may not include any post-treatment, such as post-treatment with boron, urea, thiourea, dimercaptothiadiazole, carbon disulfide, aldehydes, ketones, carboxylic acids, hydrocarbon-substituted succinic anhydrides, maleic anhydride, nitriles, epoxides, carbonates, cyclic carbonates, hindered phenol esters, and phosphorus compounds. In other embodiments, at least one of the dispersants in the detergent-free, low-ash lubricating compositions herein may be post-treated by conventional methods by reaction with any of a variety of post-treatment agents. In one approach, at least one of the dispersants in the compositions herein may be post-treated with a boron compound. Suitable post-treatment agents include boron, urea, thiourea, dimercaptothiadiazole, carbon disulfide, aldehydes, ketones, carboxylic acids, hydrocarbon-substituted succinic anhydrides, maleic anhydride, nitriles, epoxides, carbonates, cyclic carbonates, hindered phenol esters, and phosphorus compounds (see, e.g., U.S. Pat. Nos. 7,645,726, 7,214,649, 8,048,831, and 5,241,003, all of which are incorporated herein by reference in their entirety).

[0036] When post-treated with boron, the boron compound used as the post-treating reagent can be selected from boron oxide, boron halides, boric acid, and esters of boric acid in an amount to provide from about 0.1 atomic percentage of boron per mole of nitrogen composition to about 20 atomic percentages of boron for each atomic percentage of nitrogen used. The boron post-treated dispersant can contain from about 0.05 weight percent to about 2.0 weight percent, or in other approaches, from about 0.05 weight percent to about 0.7 weight percent, of boron, based on the total weight of the borated dispersant.

[0037] In other approaches, and if used, carboxylic acids can also be used as post-treating reagents and can be saturated or unsaturated mono-, di-, or poly-carboxylic acids. Examples of carboxylic acids include, but are not limited to, maleic acid, fumaric acid, succinic acid, and naphthalic diacids (e.g., 1,8-naphthalic diacid). Anhydrides can also be used as post-treating reagents and can be selected from the group consisting of mono-unsaturated anhydrides (e.g., maleic anhydride), alkyl- or alkylene-substituted cyclic anhydrides (e.g., succinic anhydride or glutamic anhydride), and aromatic carboxylic anhydrides (including naphthalic anhydride, e.g., 1,8-naphthalic anhydride).

[0038] In one embodiment, and if used, the process for post-treating a dispersant comprises first forming a succinimide product as described above, and then further reacting the succinimide product with a post-treating agent, such as a boron compound, such as boric acid. In some cases, the dispersants herein may be post-treated with more than one post-treating agent. For example, a dispersant may be post-treated with a boron compound, such as boric acid, and also post-treated with an anhydride, such as maleic anhydride and / or 1,8-naphthalic anhydride.

[0039] In embodiments, the detergent-free, low ash lubricating compositions herein may contain at least about 5 weight percent of one or more dispersants herein, or from about 5 to about 15 weight percent, preferably from about 5 to about 10 weight percent, or more preferably from about 5 to about 8 weight percent of one or more dispersants described herein.

[0040] low ash composition As noted above, the detergent-free, low-ash lubricant compositions herein are formulated to have very low levels of sulfated ash and include an additive package that provides the composition with a sulfated ash level (ASTM D874) of about 0.2 weight percent or less, about 0.1 weight percent or less, about 0.08 weight percent or less, about 0.06 weight percent or less, or about 0.05 weight percent or less (ASTM D874). In other approaches, the lubricant compositions herein may also contain about 0.01 weight percent or more sulfated ash, about 0.02 weight percent or more, about 0.3 weight percent or more, or about 0.04 weight percent or more sulfated ash (ASTM D874).

[0041] As used herein, "sulfated ash" or "SASH" refers to the amount of sulfated ash as measured using ASTM D874. Alternatively, sulfated ash may also be calculated based on the amount of metal in the lubricant. For example, sulfated ash (SASH) may be calculated based on the total metallic elements contributing to SASH in a lubricant composition, optionally adjusted by a factor for each metallic type. Metals contributing to SASH include (with adjustment factors): barium (1.7), boron (3.22), calcium (3.4), copper (1.252), lead (1.464), lithium (7.92), magnesium (4.95), manganese (1.291), molybdenum (1.5), potassium (2.33), sodium (3.09), and zinc (1.5). Specifically, the ppmw content of each metallic element present in the lubricating oil composition that is considered to contribute to sulfated ash is multiplied by its corresponding factor above, and then each metallic element / factor adjustment product is summed and the total is divided by 10,000 to calculate the weight percent of SASH in the lubricating composition. Unless otherwise specified, all sulfated ash levels herein are measured using ASTM D874.

[0042] To achieve such low sulfated ash contents, the lubricant compositions herein have a select additive package that is free of detergent additives (as described and defined above), provides an additive mixture that provides little or no calcium, magnesium, lithium, sodium, and other detergent metals, and provides only low or select amounts of other compounds that provide boron, molybdenum, and / or zinc. To this end, the lubricants herein preferably contain additives that provide not more than about 100 ppm boron (preferably not more than about 90 ppm boron or not more than about 80 ppm boron) and not more than 10 ppm each of calcium, barium, copper, lead, lithium, magnesium, zinc, sodium, molybdenum, and / or combinations thereof. In another approach, the lubricating compositions herein are substantially free of metallic detergents, and more preferably the lubricating compositions have metallic detergents providing less than about 10 ppm individual and / or total detergent metals, less than 8 ppm individual and / or total detergent metals, less than 5 ppm individual and / or total detergent metals, less than 2 ppm individual and / or total detergent metals, or less than 1 ppm individual and / or total detergent metals, or are free of detectable amounts of detergent metals, where the detergent metal is selected from calcium, magnesium, sodium, lithium, etc. In another approach, the lubricating oil compositions herein are also substantially free of metal dialkyldithiophosphates (e.g., zinc dialkyldithiophosphates), and in such context preferably have no more than about 10 ppm of zinc provided by such metal dialkyldithiophosphates.

[0043] In another embodiment, the detergent-free, low ash lubricating composition also maintains a total sulfur to total phosphorus weight ratio of less than about 2.0, preferably from about 1.0 to about 1.8, with the phosphorus and sulfur being provided by the ashless antiwear additive, as discussed above.

[0044] In still other embodiments, the detergent-free, low ash lubricating compositions herein have a Total Base Number (TBN) of at least about 4 mg KOH / g, and in other embodiments from about 4 to about 10 mg KOH / g, and in still further embodiments from about 4 to about 6 mg KOH / g, as measured in accordance with ASTM D2898.

[0045] In yet another approach, the detergent-free, low ash lubricating compositions herein have a unique relationship between the total amount of nitrogen to the TBN of the composition. For example, the compositions herein have a TBN of 100 mg KOH / g -1 >150 ppm per mg KOHg in other approaches -1 About 200 to about 350 ppm, and in other approaches, mg KOHg -1 The nitrogen to TBN ratio may be from about 280 to about 325 ppm per 1000 ppm of TBN. An example of calculating this ratio is provided in the Examples section of this specification.

[0046] In a further approach or embodiment, the detergent-free, low ash lubricating compositions herein may also have an elemental relationship between the total amounts of nitrogen, sulfur, phosphorus, and boron, characteristics that have been uniquely discovered to affect piston cleanliness in the context of detergent-free, low ash lubricating compositions, as described above. For example, in one embodiment, the detergent-free, low ash lubricating composition may have a total boron to total nitrogen, sulfur, and phosphorus weight ratio (i.e., (N+S+P) / B) of from about 20 to about 50, more preferably from about 22 to about 30, to help achieve piston cleanliness at low metal and ash contents as described herein.

[0047] lubricating oil composition The additives herein, in combination with one or more additional optional additives, may be combined with a major amount of a base oil or base oil blend (described below) of lubricating viscosity to produce a lubricating oil composition. In some approaches, the lubricating oil composition comprises about 50 weight percent or more of the base oil blend, about 60 weight percent or more, about 70 weight percent or more, or about 80 weight percent or more to about 95 weight percent or less, about 90 weight percent or less, or about 85 weight percent or less of the base oil blend, such blends being discussed further below. The lubricating compositions herein may have a KV100 of about 2 to about 15 cSt (ASTM D445), preferably about 5 to about 12 cSt, and more preferably 5 to about 10 cSt.

[0048] When the detergent-free, low-ash lubricating compositions herein are combined with the components and elemental relationships described, the lubricating compositions herein achieve a desired level of piston cleanliness without the use of traditional detergent additives. As noted above, embodiments of the lubricating compositions herein clean piston deposits with a total weighted piston deposit merit rating of at least about 4 (higher ratings indicate cleaner pistons at the end of the test) according to the Sequence IIIH Engine Test (ASTM D8111), and embodiments of the lubricating compositions herein also exhibit an average engine varnish (AES) rating of at least 8 Merit and / or an average engine sludge rating of at least 7.6 Merit according to the Sequence VH Test (ASTM D8256).

[0049] Base Oil Blend: The base oil used in the detergent-free, low ash lubricating oil compositions herein may be an oil of lubricating viscosity and is selected from any of the base oils in Groups I to V, as specified in the American Petroleum Institute (API) Base Oil Interchangeability Guidelines. The five base oil groups are as follows:

[0050] [Table 1]

[0051] Group I, Group II, and Group III are mineral oil processing stocks. Group IV base oils contain true synthetic molecular species produced by the polymerization of olefinically unsaturated hydrocarbons. Many Group V base oils are also true synthetic products and may include diesters, polyol esters, polyalkylene glycols, alkylated aromatics, polyphosphate esters, polyvinyl ethers, and / or polyphenyl ethers, but may also be natural oils such as vegetable oils. Group III base oils are derived from mineral oils, but it should be noted that the rigorous processing these fluids undergo makes their physical properties very similar to some true synthetics, such as PAOs. Therefore, oils derived from Group III base oils may be referred to in industry as synthetic fluids. Group II+ may include high viscosity index Group II.

[0052] The base oil blends used in the disclosed lubricating oil compositions can be mineral, animal, vegetable, synthetic, synthetic oil blends, or mixtures thereof. Suitable oils can be derived from hydrocracked, hydrogenated, hydrofinished, unrefined, refined, and rerefined oils, and mixtures thereof.

[0053] Unrefined oils are derived from natural, mineral, or synthetic sources with little or no further purification processing. Refined oils are similar to unrefined oils except that they have been treated with one or more purification steps, which may result in the improvement of one or more properties. Examples of suitable purification techniques include solvent extraction, secondary distillation, acid or base extraction, filtration, percolation, etc. Oils refined to edible quality may or may not be useful. Edible oils may also be called white oils. In some embodiments, the lubricating oil composition does not include edible oils or white oils.

[0054] Re-refined oils are also known as reclaimed or reprocessed oils. These oils are obtained similarly to refined oils using the same or similar processes. Often, these oils are additionally processed by techniques directed to the removal of spent additives and oil breakdown products.

[0055] Mineral oils may include oils obtained by drilling, or from plants and animals, or any mixture thereof. For example, such oils may include, but are not limited to, castor oil, lard oil, olive oil, peanut oil, corn oil, soybean oil, and linseed oil, as well as mineral lubricating oils, such as liquid petroleum oils and solvent- or acid-treated mineral lubricating oils of the paraffinic, naphthenic, or mixed paraffinic-naphthenic types. Such oils may be partially or fully hydrogenated, if desired. Oils derived from coal or shale may also be useful.

[0056] Useful synthetic lubricating oils may include hydrocarbon oils such as polymerized, oligomerized, or interpolymerized olefins (e.g., polybutylene, polypropylene, propylene-isobutylene copolymers); poly(1-hexene), poly(1-octene), trimers or oligomers of 1-decene, such as poly(1-decene) (such materials are often referred to as α-olefins), and mixtures thereof; alkyl-benzenes (e.g., dodecylbenzene, tetradecylbenzene, dinonylbenzene, di-(2-ethylhexyl)-benzene); polyphenyls (e.g., biphenyl, terphenyl, alkylated polyphenyls); diphenylalkanes, alkylated diphenylalkanes, alkylated diphenyl ethers, and alkylated diphenyl sulfides, as well as derivatives, analogs, and homologs thereof, or mixtures thereof. Polyalphaolefins are typically hydrogenated materials.

[0057] Other synthetic lubricating oils include polyol esters, diesters, liquid esters of phosphorus-containing acids (e.g., tricresyl phosphate, trioctyl phosphate, and diethyl ester of decane phosphonic acid), or polymeric tetrahydrofurans. Synthetic oils may be produced by the Fischer-Tropsch reaction and are typically hydroisomerized Fischer-Tropsch hydrocarbons or waxes. In one embodiment, the oils may be prepared by the Fischer-Tropsch gas-to-liquid synthesis procedure, as well as other gas-to-liquid oils.

[0058] A major amount of base oil included in the lubricating composition may be selected from the group consisting of Group I, Group II, Group III, Group IV, Group V, and combinations of two or more of the foregoing, but the major amount of base oil is other than the base oil resulting from the provision of additive components or viscosity index improvers in the composition. In another embodiment, a major amount of base oil included in the lubricating composition may be selected from the group consisting of Group II, Group III, Group IV, Group V, and combinations of two or more of the foregoing, but the major amount of base oil is other than the base oil resulting from the provision of additive components or viscosity index improvers in the composition.

[0059] The amount of oil of lubricating viscosity present can be the difference remaining after subtracting the sum of the amounts of performance additives, including viscosity index improvers and / or pour point depressants and / or other top treat additives, from 100% by weight. For example, the oil of lubricating viscosity may be present in the final fluid in a major amount, such as greater than about 50%, greater than about 60%, greater than about 70%, greater than about 80%, greater than about 85%, or greater than about 90% by weight.

[0060] Optional Additives: The detergent-free, low ash lubricating oil compositions herein may also contain a number of optional additives, which are described in the following paragraphs.

[0061] Boron-Containing Compounds: In accordance with the above discussion regarding boron content, the detergent-free, low-ash lubricating oil compositions herein may optionally contain one or more boron-containing compounds. Examples of boron-containing compounds include borate esters, borated fatty amines, borated epoxides, borated detergents, and borated dispersants, such as borated succinimide dispersants, as disclosed in U.S. Patent No. 5,883,057. When present, the boron-containing compounds can be used in an amount sufficient to provide up to about 8 wt. %, from about 0.01 wt. % to about 7 wt. %, from about 0.05 wt. % to about 5 wt. %, or from about 0.1 wt. % to about 3 wt. % of the lubricating oil composition.

[0062] Extreme Pressure Agents: The detergent-free, low ash lubricating compositions herein may optionally contain one or more extreme pressure agents. Oil-soluble extreme pressure (EP) agents include sulfur and chlorosulfur-containing EP agents, chlorinated hydrocarbon EP agents, and phosphorus EP agents. Examples of such EP agents include chlorinated waxes; organic sulfides and polysulfides such as dibenzyl disulfide, bis(chlorobenzyl) disulfide, dibutyl tetrasulfide, sulfurized methyl ester of oleic acid, sulfurized alkylphenols, sulfurized dipentene, sulfurized terpene, and sulfurized Diels-Alder adducts; phosphorus sulfurized hydrocarbons such as the reaction products of phosphorus sulfide with turpentine or methyl oleate; dihydrocarbyl and trihydrocarbyl phosphites, for example, phosphate esters such as dibutyl phosphite, diheptyl phosphite, dicyclohexyl phosphite, pentyl phenyl phosphite; dipentyl phenyl phosphite, tridecyl phosphite, distearyl phosphite, and polypropylene-substituted phenyl phosphites; metal thiocarbamates such as zinc dioctyldithiocarbamate and barium heptylphenol diacid; amine salts of alkyl and dialkyl phosphates, including, for example, the amine salt of the reaction product of a dialkyl dithiophosphate with propylene oxide; and mixtures thereof.

[0063] Friction Modifiers: The detergent-free and low-ash lubricating compositions herein may optionally contain one or more friction modifiers. Suitable friction modifiers may include metal-containing and metal-free friction modifiers, and may include, but are not limited to, imidazolines, amides, amines, succinimides, alkoxylated amines, alkoxylated ether amines, amine oxides, amidoamines, nitriles, betaines, quaternary amines, imines, amine salts, aminoguanidines, alkanolamides, phosphonates, metal-containing compounds, glycerol esters, sulfurized fatty compounds and olefins, sunflower oil, other naturally occurring vegetable or animal oils, dicarboxylic acid esters, esters or partial esters of polyols with one or more aliphatic or aromatic carboxylic acids, and the like.

[0064] Suitable friction modifiers may contain hydrocarbyl groups selected from linear, branched, or aromatic hydrocarbyl groups, or mixtures thereof, and may be saturated or unsaturated. The hydrocarbyl groups may be composed of carbon and hydrogen or heteroatoms such as sulfur or oxygen. The hydrocarbyl groups may range from about 12 to about 25 carbon atoms. In some embodiments, the friction modifier may be a long-chain fatty acid ester. In other embodiments, the long-chain fatty acid ester may be a mono-ester, a di-ester, or a (tri)glyceride. The friction modifier may be a long-chain fatty amide, a long-chain fatty ester, a long-chain fatty epoxide derivative, or a long-chain imidazoline.

[0065] Other suitable friction modifiers may include organic, ashless (metal-free), nitrogen-free organic friction modifiers. Such friction modifiers include esters formed by reacting carboxylic acids and anhydrides with alkanols, and may generally contain polar end groups (e.g., carboxyl or hydroxyl) covalently bonded to an oleophilic hydrocarbon chain. An example of an organic ashless, nitrogen-free friction modifier is commonly known as glycerol monooleate (GMO), which may contain mono-, di-, and tri-esters of oleic acid. Other suitable friction modifiers are described in U.S. Patent No. 6,723,685, the entire contents of which are incorporated herein by reference.

[0066] Aminic friction modifiers may include amines or polyamines. Such compounds may have hydrocarbyl groups that are linear, saturated, unsaturated, or a mixture thereof, and may contain from about 12 to about 25 carbon atoms. Further examples of suitable friction modifiers include alkoxylated amines and alkoxylated ether amines. Such compounds may have hydrocarbyl groups that are linear, saturated, unsaturated, or a mixture thereof. They may contain from about 12 to about 25 carbon atoms. Examples include ethoxylated amines and ethoxylated ether amines.

[0067] The amines and amides may be used per se or in the form of adducts or reaction products with boron compounds such as boron oxide, boron halides, metaborates, boric acid, or mono-, di-, or tri-alkylborates. Other suitable friction modifiers are described in U.S. Patent No. 6,300,291, the entire contents of which are incorporated herein by reference.

[0068] Friction modifiers may optionally be present in ranges such as from about 0% to about 10% by weight, or from about 0.01% to about 8% by weight, or from about 0.1% to about 4% by weight.

[0069] Transition Metal-Containing Compounds: In another embodiment, in accordance with the above discussion regarding total metal content, the detergent-free, low-ash lubricants herein may optionally contain a transition metal-containing compound or metalloid. Transition metals may include, but are not limited to, titanium, vanadium, copper, zinc, zirconium, molybdenum, tantalum, tungsten, and the like. Suitable metalloids include, but are not limited to, boron, silicon, antimony, tellurium, and the like.

[0070] In embodiments, the oil-soluble transition metal-containing compound may function as an antiwear agent, a friction modifier, an antioxidant, a deposit control additive, or one or more of these functions. In embodiments, the oil-soluble transition metal-containing compound may be an oil-soluble titanium compound such as a titanium(IV) alkoxide. Among the titanium-containing compounds that may be used in or for preparing the oil-soluble material in the technology of the present disclosure include, but are not limited to, various Ti(IV) compounds such as titanium(IV) oxide; titanium(IV) sulfide; titanium(IV) nitrate; titanium(IV) alkoxides, such as titanium methoxide, titanium ethoxide, titanium propoxide, titanium isopropoxide, titanium butoxide, and titanium 2-ethylhexoxide; and other titanium compounds or complexes, such as titanium phenate; titanium carboxylates, such as titanium(IV) 2-ethyl-1,3-hexanedioate, titanium citrate, or titanium oleate; and titanium(IV) (triethanolaminato)isopropoxide. Other forms of titanium encompassed by the disclosed technology include titanium phosphates, such as titanium dithiophosphates (e.g., dialkyldithiophosphates) and titanium sulfonates (e.g., alkylbenzene sulfonates), or, generally, reaction products of titanium compounds with various acidic materials to form salts, such as oil-soluble salts. Thus, titanium compounds can be derived from organic acids, alcohols, and glycols, among others. Ti compounds can also exist in dimeric or oligomeric forms containing Ti-O-Ti structures. Such titanium materials are commercially available or can be readily prepared by suitable synthetic techniques apparent to those skilled in the art. They can exist at room temperature as solids or liquids, depending on the particular compound. They can also be provided in solution form in a suitable inert solvent.

[0071] In one embodiment, titanium can be provided as a Ti-modified dispersant, such as a succinimide dispersant. Such materials can be prepared by forming a titanium mixed anhydride between a titanium alkoxide and a hydrocarbyl-substituted succinic anhydride, such as an alkenyl-(or alkyl) succinic anhydride. The resulting titanate-succinate intermediate can be used directly or reacted with any of several materials, such as (a) polyamine-based succinimide / amide dispersants having free condensable —NH functional groups; (b) the components of polyamine-based succinimide / amide dispersants, i.e., alkenyl-(or alkyl) succinic anhydrides and polyamines; or (c) hydroxy-containing polyester dispersants prepared by reacting a substituted succinic anhydride with a polyol, aminoalcohol, polyamine, or mixtures thereof. Alternatively, the titanate-succinate intermediate can be reacted with other agents, such as alcohols, amino alcohols, ether alcohols, polyether alcohols or polyols, or fatty acids, and the product can be used directly to impart Ti to lubricants or further reacted with a succinic dispersant as described above. As an example, one part (mole) of tetraisopropyl titanate can be reacted with about two parts (mole) of polyisobutene-substituted succinic anhydride at 140-150°C for 5-6 hours to provide a titanium-modified dispersant or intermediate. The resulting material (30 g) can be further reacted with a succinimide dispersant from a polyisobutene-substituted succinic anhydride and polyethylene polyamine mixture (127 grams + diluent oil) at 150°C for 1.5 hours to produce a titanium-modified succinimide dispersant.

[0072] Another titanium-containing compound is titanium alkoxide and C6-C 25 The reaction product may be a reaction product with a carboxylic acid. The reaction product has the following formula:

[0073] [ka] wherein n is an integer selected from 2, 3, and 4, and R is a hydrocarbyl group containing from about 5 to about 24 carbon atoms, or

[0074] [ka] wherein m+n=4, n ranges from 1 to 3, R4 is an alkyl moiety having from 1 to 8 carbon atoms, R1 is selected from a hydrocarbyl group containing from about 6 to 25 carbon atoms, and R2 and R3 are the same or different and are selected from a hydrocarbyl group containing from 1 to 6 carbon atoms; or the titanium compound may be represented by the following formula:

[0075] [ka] wherein x ranges from 0 to 3; R1 is selected from hydrocarbyl groups containing about 6 to 25 carbon atoms; R2 and R3 are the same or different and are selected from hydrocarbyl groups containing about 1 to 6 carbon atoms; and R4 is selected from H, C6 to C6 25 The carboxylic acid moiety is selected from the group consisting of:

[0076] Suitable carboxylic acids may include, but are not limited to, caproic acid, caprylic acid, lauric acid, myristic acid, palmitic acid, stearic acid, arachic acid, oleic acid, erucic acid, linoleic acid, linolenic acid, cyclohexanecarboxylic acid, phenylacetic acid, benzoic acid, neodecanoic acid, and the like.

[0077] In embodiments, the oil-soluble titanium compound may be present in the lubricating oil composition in an amount to provide from about 0 to about 3000 ppm by weight of titanium, or from 25 to about 1500 ppm by weight of titanium, or from about 35 ppm to about 500 ppm by weight of titanium, or from about 50 ppm to about 300 ppm.

[0078] Viscosity index improver: The detergent-free, low-ash lubricating oil compositions herein may optionally contain one or more viscosity index improvers, such as dispersant olefin copolymer viscosity index improvers. Suitable viscosity index improvers may include polyolefins, olefin copolymers, ethylene / propylene copolymers, polyisobutene, hydrogenated styrene-isoprene polymers, styrene / maleic acid ester copolymers, hydrogenated styrene / butadiene copolymers, hydrogenated isoprene polymers, alpha-olefin maleic anhydride copolymers, polymethacrylates, polyacrylates, polyalkylstyrenes, hydrogenated alkenylaryl conjugated diene copolymers, or mixtures thereof. Viscosity index improvers may include star polymers, suitable examples of which are described in U.S. Patent Application Publication No. 20120101017(A1).

[0079] The lubricating oil compositions herein may optionally contain one or more dispersant viscosity index improvers in addition to or in place of the viscosity index improver. Suitable viscosity index improvers may include functionalized polyolefins, such as ethylene-propylene copolymers functionalized with the reaction product of an acylating agent (such as maleic anhydride) and an amine, amine-functionalized polymethacrylates, or esterified maleic anhydride-styrene copolymers reacted with amines.

[0080] In one approach, a suitable dispersant olefin copolymer viscosity index improver comprises the reaction product of an acylated olefin copolymer and a polyamine, where the acylated olefin copolymer comprises an olefin copolymer having from about 0.3 to about 0.75 carboxylic acid groups grafted per 1000 number average molecular weight units of the olefin copolymer, the olefin copolymer having a number average molecular weight of from about 40,000 to about 150,000, and the polyamine is an N-arylphenylenediamine. In an optional approach, the detergent-free, low-ash lubricating composition comprises from about 1 weight percent to about 4 weight percent of the dispersant olefin copolymer viscosity index improver.

[0081] Other optional additives: Other additives may be selected to perform one or more functions required in a lubricating fluid. Furthermore, one or more of the additives mentioned may be multifunctional and may provide functions in addition to or other than those specified and described herein. The other performance additives may be in addition to the additives specified in this disclosure and / or may include one or more of metal deactivators, viscosity index improvers, ashless TBN boosters, friction modifiers, antiwear agents, corrosion inhibitors, rust inhibitors, dispersants, dispersant viscosity index improvers, extreme pressure agents, antioxidants, foam suppressants, demulsifiers, emulsifiers, pour point depressants, seal swell agents, and mixtures thereof. Typically, a fully formulated lubricating oil will contain one or more of these performance additives, subject to the above discussion regarding the components, amounts, and relationships of the various composition components.

[0082] Suitable metal deactivators may include derivatives of benzotriazole (typically tolyltriazole), dimercaptothiadiazole derivatives, 1,2,4-triazole, benzimidazole, 2-alkyldithiobenzimidazole, or 2-alkyldithiobenzothiazole; foam suppressors including copolymers of ethyl acrylate, 2-ethylhexyl acrylate, and optionally vinyl acetate; demulsifiers including trialkyl phosphate, polyethylene glycol, polyethylene oxide, polypropylene oxide, and (ethylene oxide-propylene oxide) polymers; pour point depressants including esters of maleic anhydride-styrene, polymethacrylate, polyacrylate, or polyacrylamide.

[0083] Suitable suds suppressors include silicon-based compounds such as siloxanes.

[0084] Suitable pour point depressants may include polymethyl methacrylate or mixtures thereof. The pour point depressant may be present in an amount sufficient to provide from about 0 wt % to about 1 wt %, from about 0.01 wt % to about 0.5 wt %, or from about 0.02 wt % to about 0.04 wt %, based on the final weight of the lubricating oil composition.

[0085] Suitable additional rust inhibitors can be a single compound or a mixture of compounds that have corrosion-inhibiting properties for ferrous metal surfaces. Additional rust inhibitors can be provided as long as they do not compete with the selected corrosion inhibitor discussed above. In addition to those listed above, non-limiting examples of rust inhibitors include oil-soluble high molecular weight organic acids such as 2-ethylhexanoic acid, lauric acid, myristic acid, palmitic acid, oleic acid, linoleic acid, linolenic acid, behenic acid, and cerotic acid, as well as oil-soluble polycarboxylic acids, including dimer and trimer acids such as those produced from tall oil fatty acid, oleic acid, and linoleic acid. Other suitable corrosion inhibitors include long-chain alpha- and omega-dicarboxylic acids in the molecular weight range of about 600 to about 3000, and alkenyl succinic acids in which the alkenyl group contains about 10 or more carbon atoms, such as tetrapropenyl succinic acid, tetradecenyl succinic acid, and hexadecenyl succinic acid. Another useful type of acidic corrosion inhibitor is the half ester of an alkenyl succinic acid having from about 8 to about 24 carbon atoms in the alkenyl group with an alcohol, such as a polyglycol. The corresponding half amides of such alkenyl succinic acids are also useful. Useful rust inhibitors are high molecular weight organic acids.

[0086] When present, the rust inhibitor may be used in an amount sufficient to provide from about 0% to about 5%, from about 0.01% to about 3%, or from about 0.1% to about 2% by weight based on the final weight of the lubricating oil composition.

[0087] In general terms, suitable detergent-free, low ash lubricants herein may contain additive components in the ranges listed in the table below.

[0088] [Table 2]

[0089] The percentages of each component above represent the weight percent of each component based on the weight of the final lubricating oil composition. The remainder of the lubricating oil composition consists of one or more base oils. The additives used in formulating the compositions described herein can be blended into the base oil individually or in various partial combinations. However, it may be preferred to blend all of the components simultaneously using an additive concentrate (i.e., additives plus a diluent such as a hydrocarbon solvent). Fully formulated lubricants conventionally contain an additive package, referred to herein as a dispersant / inhibitor package or DI package, that supplies the properties required in the formulation.

[0090] The lubricants herein are configured for use in various types of lubricants, such as automotive lubricants and / or greases, internal combustion engine oils, hybrid engine oils, electric engine lubricants, drivetrain lubricants, transmission lubricants, gear oils, hydraulic lubricants, tractor hydraulic fluids, metal working fluids, turbine engine lubricants, stationary engine lubricants, tractor lubricants, motorcycle lubricants, power steering fluids, clutch fluids, axle fluids, wet brake fluids, and the like. Suitable engine types may include, but are not limited to, heavy-duty diesel, passenger car, light-duty diesel, medium-speed diesel, or marine engines. The internal combustion engine may be a diesel-fueled engine, a gasoline-fueled engine, a natural gas-fueled engine, a biofuel engine, a diesel / bio-fueled blend engine, a gasoline / bio-fueled blend-fuel engine, an alcohol-fueled engine, a gasoline / alcohol-fueled blend engine, a compressed natural gas (CNG)-fueled engine, or a mixture thereof. The diesel engine may be a compression-ignition engine. The gasoline engine may be a spark-ignition engine. The internal combustion engine may also be used in combination with electric or battery power. Engines configured in this manner are commonly known as hybrid engines. The internal combustion engine may be a two-stroke, four-stroke, or rotary engine. Suitable internal combustion engines include marine diesel engines (such as inland marine), aviation piston engines, light-duty diesel engines, and motorcycle, automobile, locomotive, and truck engines. The engine may be coupled with a turbocharger.

[0091] The terms "oil composition," "lubrication composition," "lubricating oil composition," "lubricating oil," "lubricant composition," "lubricating composition," "fully formulated lubricant composition," "lubricant," "crankcase oil," "crankcase lubricant," "engine oil," "engine lubricant," "motor oil," and "motor lubricant" are considered to be synonymous and fully interchangeable terms that refer to a finished lubricant product that includes a major amount of a base oil plus a minor amount of an additive composition.

[0092] As used herein, the terms "additive package," "additive concentrate," "additive composition," "engine oil additive package," "engine oil additive concentrate," "crankcase additive package," "crankcase additive concentrate," "motor oil additive package," and "motor oil concentrate" are considered synonymous and fully interchangeable terms that refer to that portion of a lubricating oil composition that excludes a major amount of a base oil stock blend. The additive package may or may not include a viscosity index improver or a pour point depressant.

[0093] The term "overbased" refers to metal salts, such as metal salts of sulfonates, carboxylates, salicylates, and / or phenates, in which the amount of metal present exceeds the stoichiometric amount. Such salts may have conversion levels greater than 100% (i.e., they may contain more than 100% of the theoretical amount of metal required to convert the acid to its "standard" or "neutral" salt). The expression "metal ratio," often abbreviated as MR, is used to indicate the ratio of the total chemical equivalents of metal in an overbased salt to the chemical equivalents of metal in a neutral salt, according to known chemical reactivity and stoichiometry. In standard or neutral salts, the metal ratio is 1; in overbased salts, the MR is greater than 1. These are commonly referred to as overbased, highly based, or superbased salts and may be salts of organic sulfur acids, carboxylic acids, salicylates, sulfonates, and / or phenols.

[0094] The term "alkaline earth metals" refers to calcium, barium, magnesium, and strontium, while the term "alkali metals" refers to lithium, sodium, potassium, rubidium, and cesium.

[0095] As used herein, the terms "hydrocarbyl" or "hydrocarbyl substituent" or "hydrocarbyl group" are used in their ordinary sense, as is well known to those skilled in the art. Specifically, they refer to a group having a carbon atom directly attached to the remainder of the molecule and having a predominantly hydrocarbon character. Each hydrocarbyl group is independently selected from hydrocarbon substituents, where the substituted hydrocarbon substituents contain one or more of halo, hydroxyl, alkoxy, mercapto, nitro, nitroso, amino, pyridyl, furyl, imidazolyl, oxygen, and nitrogen, and no more than two non-hydrocarbon substituents are present for every 10 carbon atoms in the hydrocarbyl group.

[0096] As used herein, the term "hydrocarbylene substituent" or "hydrocarbylene group" is used in its ordinary sense, as is well known to those skilled in the art. Specifically, it refers to a group that is directly attached to the remainder of the molecule by carbon atoms at two locations and has a predominantly hydrocarbon character. Each hydrocarbylene group is independently selected from divalent hydrocarbon substituents, including halo, alkyl, aryl, alkylaryl, arylalkyl, hydroxyl, alkoxy, mercapto, nitro, nitroso, amino, pyridyl, furyl, imidazolyl, oxygen, and nitrogen, and no more than two non-hydrocarbon substituents are present for every 10 carbon atoms in the hydrocarbylene group.

[0097] As used herein, the term "weight percent," unless expressly stated otherwise, means the percentage that the recited component represents relative to the weight of the entire composition.

[0098] As used herein, the terms "ppm" or "ppmw" refer to parts per million by weight unless expressly stated otherwise.

[0099] The terms "soluble," "oil-soluble," or "dispersible" as used herein may, but do not necessarily, indicate that a compound or additive is soluble, dissolvable, miscible, or capable of being suspended in oil in any proportion. However, the terms do mean that they are, for example, soluble, suspendable, dissolvable, or stably dispersible in oil to a sufficient degree to exert their intended effect in the environment in which the oil is used. Furthermore, if desired, the incorporation of other additives may also allow for the incorporation of higher levels of the specific additive.

[0100] As used herein, the term "TBN" is used to indicate the total base number in mg KOH / g as measured by the method of ASTM D2896.

[0101] As used herein, the term "alkyl" refers to straight, branched, cyclic, and / or substituted saturated chain moieties of about 1 to about 100 carbon atoms. As used herein, the term "alkenyl" refers to straight, branched, cyclic, and / or substituted unsaturated chain moieties of about 3 to about 10 carbon atoms. As used herein, the term "aryl" refers to monocyclic and polycyclic aromatic compounds that may contain alkyl, alkenyl, alkylaryl, amino, hydroxyl, alkoxy, halo substituents, and / or heteroatoms, including, but not limited to, nitrogen, oxygen, and sulfur.

[0102] As used herein, "post-reacted" or "post-treated" refers to a component that is further reacted or treated, for example, with boron, phosphorus, and / or maleic anhydride, and may refer to a dispersant in which primary and / or secondary amines are further reacted with such compounds to convert at least a portion of such amines to tertiary amines. Such subsequent reactions or treatments are further described in U.S. Pat. No. 5,241,003, which is incorporated herein by reference. Conversely, a "non-post-reacted" or "non-post-treated" component has not been subjected to such further treatment, reaction, and / or processing, and in the context of a dispersant, contains a certain amount of primary and / or secondary amines.

[0103] The molecular weight of any embodiment herein can be determined using a gel permeation chromatography (GPC) instrument from Waters or similar instrumentation, and data processed with Waters Empower Software or similar software. The GPC instrument can be equipped with a Waters Separation Module and a Waters Refractive Index Detector (or similar optional instrumentation). GPC operating conditions can include a guard column, four Agilent PLgel columns (300 x 7.5 mm long, 5 μm particle size, and pore sizes ranging from 100 to 10,000 Å), and a column temperature of approximately 40°C. Unstabilized HPLC-grade tetrahydrofuran (THF) can be used as the solvent at a flow rate of 1.0 mL / min. The GPC instrument can be calibrated with commercially available polystyrene (PS) standards with narrow molecular weight distributions ranging from 500 to 380,000 g / mol. The calibration curve can be extrapolated for samples with masses less than 500 g / mol. Samples and PS standards are dissolved in THF at concentrations of 0.1 to 0.5% by weight and can be used without filtration. GPC measurements are also described in U.S. Pat. No. 5,266,223, which is incorporated herein by reference. The GPC method additionally provides molecular weight distribution information; see, for example, W.W. Yau, J.J. Kirkland, and D.D. Bly, "Modern Size Exclusion Liquid Chromatography," John Wiley and Sons, New York, 1979, which is incorporated herein by reference.

[0104] As used herein, "sulfated ash" or "SASH" refers to the amount of sulfated ash as measured using ASTM D874. Alternatively, sulfated ash may also be calculated based on the amount of metal in the lubricant. For example, sulfated ash (SASH) may be calculated based on the total metallic elements contributing to SASH in a lubricant composition, optionally adjusted by a factor for each metallic type. Metals contributing to SASH include (with adjustment factors): barium (1.7), boron (3.22), calcium (3.4), copper (1.252), lead (1.464), lithium (7.92), magnesium (4.95), manganese (1.291), molybdenum (1.5), potassium (2.33), sodium (3.09), and zinc (1.5). Specifically, the ppmw content of each metallic element present in the lubricating oil composition that is considered to contribute to sulfated ash is multiplied by its corresponding factor above, and then each metallic element / factor adjustment product is summed and the total is divided by 10,000 to calculate the weight percent of SASH in the lubricating composition. Unless otherwise specified, all sulfated ash levels herein are measured using ASTM D874. [Example]

[0105] A better understanding of the present disclosure and its many advantages may be clarified with the following examples. The following examples are illustrative and not limiting in scope or spirit. Those skilled in the art will readily understand that variations of the components, methods, steps, and devices described in these examples can be used. Unless otherwise stated or apparent from the context of the following examples and discussion throughout this disclosure, all percentages, ratios, and parts stated in this disclosure are by weight.

[0106] To demonstrate how detergent-free, low-ash lubricants, as defined herein, can achieve suitable performance as passenger car motor oils when elemental relationships are selected rather than the incorporation of new additives, passenger car motor oils of the present invention and comparative passenger car motor oils were evaluated for high temperature deposits (TEOST-33), as measured in accordance with ASTM D6335, weighted piston deposits (WPD) in the Sequence IIIH test of ASTM D8111, and average engine sludge (AES) and average engine varnish (AEV) in the Sequence VH test of ASTM D8256. All passenger car motor oils in this example contained similar amounts of antifoam additive, process oil, pour point depressant, viscosity modifier, and Group III base oil to form lubricants having kV100 viscosities (ASTM D445) of about 10 to about 12 cSt. The comparative lubricants and lubricants of the present invention also contained the following additives in Table 1 and, when included, the fluid relationships in Table 2 below. Dispersant Disp-1: a succinimide dispersant from polyisobutylene having a number average molecular weight of about 1000 to about 2000 and post-treated with a boron compound. Dispersant Disp-2: A succinimide dispersant derived from polyisobutene having a number average molecular weight greater than about 2000. Dispersant Disp-3: A succinimide dispersant derived from polyisobutylene having a number average molecular weight of 1000 to about 2000. Detergent 1 (Det-1): An overbased calcium sulfonate with a TBN of approximately 300. Detergent 2 (Det-2): An overbased magnesium sulfonate with a TBN of approximately 400. Antiwear 1 (AW1): 3-[[bis(2-methylpropoxy)phosphinothioyl]thio]-2-methyl-propanoic acid. Antiwear 2 (AW2): A zinc dialkyldithiophosphate in which 100% of the alkyl groups are derived from primary alcohols. Antiwear 3 (AW3): A zinc dialkyldithiophosphate in which 100% of the alkyl groups are derived from secondary alcohols. Antioxidant 1 (AO1): Di-alkyldiphenylamine antioxidant. Antioxidant 2 (AO2): Phenolic ester antioxidant. · Antioxidant 3 (AO3): A molybdenum-containing antioxidant. Antioxidant 4 (AO4): A sulfur-containing antioxidant. Viscosity Modifier (DOCP1): A dispersant olefin copolymer viscosity modifier grafted with N-arylphenylenediamine having a number average MW of 40,000 to 150,000.

[0107] [Table 3]

[0108] [Table 4]

[0109] [Table 5]

[0110] It should be noted that, as used in this specification and the appended claims, the singular forms "a," "an," and "the" include plural referents unless expressly and unambiguously limited to one referent. Thus, for example, reference to "antioxidants" includes two or more different antioxidants. As used herein, the term "comprises" and grammatical variations thereof are intended to be open-ended such that the recitation of items in a list does not exclude other similar items that may be substituted for or added to the items in the list.

[0111] For purposes of this specification and the appended claims, unless otherwise indicated, all numbers expressing quantities, percentages, or proportions, and other numerical values ​​used in the specification and claims should be understood in all instances to be modified by the term "about." Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and appended claims are approximations that may vary depending upon the desired properties sought to be obtained by the present disclosure. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.

[0112] It is understood that each component, compound, substituent, or parameter disclosed herein should be construed as disclosed for use alone or in combination with one or more of any and all other components, compounds, substituents, or parameters disclosed herein.

[0113] It is further understood that each range disclosed herein should be construed as a disclosure of each specific value within the disclosed range having the same number of significant digits. Thus, for example, a range of 1 to 4 should be construed as an explicit disclosure of not only the values ​​1, 2, 3, and 4, but also any range of such values.

[0114] It should be further understood that each lower limit of each range disclosed herein should be interpreted as being disclosed in combination with each upper limit of each range and each specific value within each range for the same component, compound, substituent, or parameter. Thus, the present disclosure should be interpreted as a disclosure of all ranges derived by combining each lower limit of each range with each upper limit of each range, or each specific value within each range, or by combining each upper limit of each range with each specific value within each range. It should also be further understood that any range between the endpoints within a broad range is also contemplated herein. Thus, a range of 1 to 4 also means ranges of 1 to 3, 1 to 2, 2 to 4, 2 to 3, etc.

[0115] Furthermore, a specific amount / value of a component, compound, substituent, or parameter disclosed in the description or examples should be construed as a disclosure of either a lower or upper limit of a range and, therefore, can be combined with any other lower or upper limit or specific amount / value in a range for the same component, compound, substituent, or parameter disclosed elsewhere in this application to form a range for that component, compound, substituent, or parameter.

[0116] While particular embodiments have been described, alternatives, modifications, variations, improvements, and substantial equivalents may occur that are not presently anticipated or presently unforeseeable to applicants or others skilled in the art. Accordingly, the appended claims, as filed and as they may be amended, are intended to embrace all such alternatives, modifications, variations, improvements, and substantial equivalents.

Claims

1. 1. A detergent-free, low ash lubricating composition comprising: one or more base oils of lubricating viscosity; less than about 0.2 weight percent total sulfated ash (SASH) as measured by ASTM D874; one or more succinimide dispersants derived from polyisobutylene having a number average molecular weight of at least about 1000, said succinimide dispersants each having a maximum of about 2 weight percent nitrogen, and at least one of said succinimide dispersants being post-treated with a boron compound; one or more ashless antiwear additives; one or more antioxidants; a total base number (TBN) of at least about 4 according to ASTM D2896; at least about 1000 ppm nitrogen; not more than 100 ppm boron; not more than 800 ppm sulfur; a sulfur to phosphorus ratio of not more than 2.0; and a nitrogen to TBN ratio of not less than about 150; 1. A detergent-free, low ash lubricating composition, wherein the detergent-free, low ash lubricating composition is substantially free of calcium, barium, copper, lead, lithium, magnesium, sodium, molybdenum, zinc, and potassium.

2. 10. The detergent-free, low ash lubricating composition of claim 1, further comprising less than about 10 ppm of each of calcium, barium, copper, lead, lithium, magnesium, sodium, molybdenum, zinc, and potassium.

3. 3. The detergent-free, low ash lubricating composition of claim 2, further comprising up to about 500 ppm phosphorus and up to about 600 ppm sulfur.

4. 4. The detergent-free, low ash lubricating composition of claim 3, wherein said composition comprises at least about 6 times more of said one or more antioxidants than said one or more ashless antiwear additives.

5. 5. The detergent-free, low-ash lubricating composition of claim 4, wherein the total sulfated ash (SASH) is less than about 0.1 weight percent as measured in accordance with ASTM D874.

6. 10. The detergent-free, low ash lubricating composition of claim 1, wherein the one or more ashless antiwear additives comprise one or more ashless dialkyldithiophosphate antiwear additives.

7. The one or more ashless dialkyldithiophosphate antiwear additives have the structure of Formula I or a salt thereof: 【Chemistry 1】 In the formula, R ４ and R ５ are independently a C3 to C8 linear or branched alkyl group, and R ６ is —H or —CH ３ 7. The detergent-free, low ash lubricating composition of claim 6, wherein

8. 10. The detergent-free, low ash lubricating composition of claim 1, wherein the one or more antioxidants comprise an aminic antioxidant, a hindered phenolic antioxidant, or a combination thereof.

9. 9. The detergent-free, low ash lubricating composition of claim 8, wherein the aminic antioxidant is selected from the group comprising aromatic amines, alkylated diphenylamines, alkyldiphenylamines, di-alkyldiphenylamines, octyldiphenylamines, di-octyldiphenylamines, phenyl-alpha-naphthylamines, alkylated phenyl-alpha-naphthylamines, hindered non-aromatic amines, or combinations thereof.

10. 2. The detergent-free, low ash lubricating composition of claim 1, wherein the one or more succinimine dispersants comprise: (i) a succinimide dispersant derived from polyisobutylene having a number average molecular weight of from about 1000 to about 2000 and post-treated with a boron compound; (ii) a succinimide dispersant derived from polyisobutylene having a number average molecular weight greater than about 2000; and (iii) a succinimide derived from polyisobutylene having a number average molecular weight of from 1000 to about 2000.

11. 10. The detergent-free, low-ash lubricating composition of claim 1, wherein greater than 50 weight percent of the total nitrogen is provided by the one or more antioxidants.

12. 10. The detergent-free, low ash lubricating composition of claim 1, further comprising a dispersant olefin copolymer viscosity index improver comprising the reaction product of an acylated olefin copolymer and a polyamine, wherein the acylated olefin copolymer comprises an olefin copolymer having from about 0.3 to about 0.75 carboxylic acid groups grafted per 1000 number average molecular weight units of the olefin copolymer, the olefin copolymer having a number average molecular weight of from about 40,000 to about 150,000, and the polyamine is an N-arylphenylenediamine.

13. 13. The detergent-free, low ash lubricating composition of claim 12, wherein the lubricating composition comprises from about 1 weight percent to about 4 weight percent of the dispersant olefin copolymer viscosity index improver.

14. 2. The detergent-free, low ash lubricating composition of claim 1, wherein the total amount of the nitrogen, sulfur, and phosphorus relative to the amount of the boron (N+S+P) / B is from about 20 to about 50.

15. 10. The detergent-free, low ash lubricating composition of claim 1, wherein the lubricating composition cleans piston deposits with a total weighted piston deposit merit rating of at least about 4 according to the Sequence IIIH Engine Test (ASTM D8111), and the lubricating composition exhibits an average engine varnish (AES) rating of at least 8 Merit and / or an average engine sludge rating of at least 7.6 Merit according to the Sequence VH Test (ASTM D8256).

16. 1. A method of lubricating a combustion engine with a detergent-free, low ash lubricating composition, said method comprising: lubricating a combustion engine with the detergent-free, low ash lubricating composition, the detergent-free, low ash lubricating composition comprising one or more base oils of lubricating viscosity, one or more succinimide dispersants derived from polyisobutylene having a number average molecular weight of at least about 1000 and a total sulfated ash (SASH) content of less than about 0.2 weight percent as measured by ASTM D874, the succinimide dispersants each having a maximum of about 2 weight percent nitrogen, and at least one of the succinimide dispersants being post-treated with a boron compound, one or more ashless antiwear additives, one or more antioxidants, and one or more succinimide dispersants derived from polyisobutylene having a number average molecular weight of at least about 1000, the succinimide dispersants each having a maximum of about 2 weight percent nitrogen, and at least one of the succinimide dispersants being post-treated with a boron compound; one or more ashless antiwear additives; one or more antioxidants; and one or more base oils of lubricating viscosity having a total sulfated ash (SASH) content of less than about 0.2 weight percent as measured by ASTM D874. D2896, a total base number (TBN) of at least about 4, at least about 1000 ppm nitrogen, not more than 100 ppm boron, not more than 800 ppm sulfur, a sulfur-to-phosphorus ratio of not more than 2.0, and a nitrogen-to-TBN ratio of not less than about 150, wherein the detergent-free, low ash lubricating composition is substantially free of calcium, barium, copper, lead, lithium, magnesium, sodium, molybdenum, zinc, and potassium; The method of claim 1, wherein the lubricating composition cleans piston deposits with a total weighted piston deposit merit rating of at least about 4 according to the Sequence IIIH Engine Test (ASTM D8111), and the lubricating composition exhibits an average engine varnish (AES) rating of at least 8 Merit and / or an average engine sludge rating of at least 7.6 Merit according to the Sequence VH Test (ASTM D8256).

17. 17. The method of claim 16, further comprising less than about 10 ppm of each of calcium, barium, copper, lead, lithium, magnesium, sodium, molybdenum, zinc, and potassium.

18. 20. The method of claim 17, further comprising about 500 ppm or less of phosphorus and about 600 ppm or less of sulfur.

19. 20. The method of claim 19, wherein the composition comprises at least about 6 times more of the one or more antioxidants than the one or more ashless antiwear additives.

20. 20. The method of claim 19, wherein the total sulfated ash (SASH) as measured in accordance with ASTM D874 is less than about 0.1 weight percent.

21. 17. The method of claim 16, wherein the one or more ashless antiwear additives comprise one or more ashless dialkyldithiophosphate antiwear additives.

22. The one or more ashless dialkyldithiophosphate antiwear additives have the structure of Formula I or a salt thereof: 【Chemistry 2】 In the formula, R ４ and R ５ are independently a C3 to C8 linear or branched alkyl group, and R ６ is —H or —CH ３ 22. The method of claim 21, wherein:

23. 17. The method of claim 16, wherein the one or more antioxidants comprise an amine antioxidant, a hindered phenolic antioxidant, or a combination thereof.

24. 24. The method of claim 23, wherein the aminic antioxidant is selected from the group comprising aromatic amines, alkylated diphenylamines, alkyldiphenylamines, di-alkyldiphenylamines, octyldiphenylamines, di-octyldiphenylamines, phenyl-alpha-naphthylamines, alkylated phenyl-alpha-naphthylamines, hindered non-aromatic amines, or combinations thereof.

25. 17. The method of claim 16, wherein the one or more succinimine dispersants comprise: (i) a succinimide dispersant derived from polyisobutylene having a number average molecular weight of from about 1000 to about 2000 and post-treated with a boron compound; (ii) a succinimide dispersant derived from polyisobutylene having a number average molecular weight greater than about 2000; and (iii) a succinimide derived from polyisobutylene having a number average molecular weight of from 1000 to about 2000.

26. 17. The method of claim 16, wherein greater than 50 weight percent of the total nitrogen is provided by the one or more antioxidants.

27. 17. The method of claim 16, further comprising a dispersant olefin copolymer viscosity index improver comprising the reaction product of an acylated olefin copolymer and a polyamine, wherein the acylated olefin copolymer comprises an olefin copolymer having from about 0.3 to about 0.75 carboxylic acid groups grafted per 1000 number average molecular weight units of the olefin copolymer, the olefin copolymer having a number average molecular weight of from about 40,000 to about 150,000, and the polyamine is an N-arylphenylenediamine.

28. 17. The method of claim 16, wherein the lubricating composition comprises from about 1 weight percent to about 4 weight percent of the dispersant olefin copolymer viscosity index improver.

29. 17. The method of claim 16, wherein the total amount of the nitrogen, sulfur, and phosphorus relative to the amount of the boron (N+S+P) / B is about 20 to about 50.

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