WO2015095051A1

WO2015095051A1 - Lubricating compositions and associated methods of use

Info

Publication number: WO2015095051A1
Application number: PCT/US2014/070350
Authority: WO
Inventors: Cheng Chen
Original assignee: Shell Oil Company; Shell Internationale Research Maatschappij B.V.
Priority date: 2013-12-17
Filing date: 2014-12-15
Publication date: 2015-06-25

Abstract

A lubricating composition for use in the crankcase of an engine comprising a base oil and a dialkyl sulfosuccinate salt. The lubricating compositions of the present invention have been found to exhibit improved piston cleanliness and to reduce high temperature deposit formation.

Description

LUBRICATING COMPOSITIONS AND ASSOCIATED METHODS OF USE

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Application No. 61/916,973, filed on December 17, 2013, the entire disclosure of which is hereby incorporated by reference.

BACKGROUND

[0002] Government regulations and market demands continue to emphasize conservation of fossil fuels in the transportation industry. There is increasing demand for more fuel-efficient vehicles in order to meet C0₂ emissions reductions targets. Therefore, any incremental improvement in fuel economy (FE) is of great importance in the automotive sector. Lubricants can play an important role in reducing a vehicle's fuel consumption and there is a continuing need for improvements in fuel economy performance, in particular long term or sustained fuel economy performance, of lubricant compositions contained within an internal combustion engine.

[0003] Similarly, auto manufacturers and governments continue to request improved fuel economy performance and robustness of motor oils, including improvements in high temperature oxidation, reducing high temperature piston deposit formation, reducing engine sludge formation, and improving wear. Reductions in piston deposit formation and engine sludge are also important in extending engine life. Generally, detergents and dispersants are added to engine lubricating oil compositions to minimize piston deposit and engine sludge formation. Such detergents and dispersants typically contain hydrophobic hydrocarbon tails and polar heads. Normally the treat rate of dispersants is 3-6%. Addition of detergents and dispersants, as is currently practiced, may reduce or remove sludge formation. However, such additives generally significantly increase the kinematic viscosity of the lubricant composition, thereby reducing fuel economy. Further, addition of detergents and/or dispersants should have no adverse effect on fluoroelastomer compatibility when the engine lubricating oil composition is to be used in an engine with seal material that comprises a fluorinated polymer. Especially crankcase lubricants should be compatible with fluoroelastomers.

[0004] There is also a need to provide lubricating compositions for use in the crankcase of an engine, wherein the compositions provide a reduction in engine deposits and sludge (hereafter referred to as "deposits"), piston cleanliness benefits, and/or improved dispersancy, as well as potential long term or sustained fuel economy benefits.

SUMMARY

[0005] The present invention generally relates to a lubricating composition comprising a base oil and one or more additives for particular use in the crankcase of an engine. In particular, the present invention relates to a lubricating composition comprising a base oil and one or more additives for use in the crankcase of an engine which may minimize deposit build-up in engines, provide improved piston cleanliness, as well as sustained fuel economy and/or improved dispersancy.

[0006] Accordingly, in one embodiment, the present invention provides a lubricating composition for use in the crankcase of an engine comprising a base oil and a dialkyl sulfosuccinate salt.

[0007] In another embodiment, the present invention provides a method comprising: introducing a lubricant composition comprising a base oil and a dialkyl sulfosuccinate salt into a crankcase of an engine.

[0008] In yet another embodiment, the present invention provides the use of a lubricating composition comprising a base oil and a dialkyl sulfosuccinate salt in the crankcase of an engine, in order to improve sustained fuel economy properties while obtaining improved piston cleanliness properties and/or improved dispersancy properties.

[0009] The features and advantages of the present disclosure will be apparent to those skilled in the art. While numerous changes may be made by those skilled in the art, such changes are within the spirit of the invention.

DETAILED DESCRIPTION

[0010] As used herein, the term "sustained fuel economy" means good fuel economy throughout the oil drain interval. A lubricant exhibiting sustained fuel economy has comparable good fuel economy performance throughout the oil drain interval as at the start.

[0011] While not wishing to be limited by theory, it is believed that the improved wear protection provided by the lubricant compositions of the present invention allow for the use of lower viscosity oils. Similarly, it is believed that the lubricant compositions of the present invention may also provide a reduction in deposits without significantly increasing the kinematic viscosity. Furthermore, it is believed that the lubricant compositions of the present invention may exhibit improved soot dispersancy, which leads to a lower viscosity increase in the lubricating oil compositions over the oil drain interval and hence an improvement in sustained fuel economy properties.

A. Base Oil

[0012] There are no particular limitations regarding the base oil used in the lubricating compositions, and various conventional mineral oils, synthetic oils, as well as any base oil which belongs to Group I, Group II, Group III, Group IV, Group V and so on of the API (American Petroleum Institute) base oil categories, may be conveniently used. These API categories are defined in API Publication 1509, 15th Edition, Appendix E, April 2002. Furthermore, the base oil may conveniently comprise mixtures of one or more mineral oils and/or one or more synthetic oils; thus, the term "base oil" may refer to a mixture comprising more than one base oil.

[0013] Mineral oils include liquid petroleum oils and solvent-treated or acid-treated mineral lubricating oil of the paraffinic, naphthenic, or mixed paraffinic/naphthenic type which may be further refined by hydrofinishing processes and/or dewaxing.

[0014] Naphthenic base oils have low viscosity index (VI) (generally 40-80) and a low pour point. Such base oils are produced from feedstocks rich in naphthenes and low in wax content and are used mainly for lubricants in which color and color stability are important, and VI and oxidation stability are of secondary importance.

[0015] Paraffinic base oils have higher VI (generally >95) and a high pour point.

Such base oils are produced from feedstocks rich in paraffins, and are used for lubricants in which VI and oxidation stability are important.

[0016] Fischer- Tropsch derived base oils may be used as the base oil. By the term "Fischer- Tropsch derived" is meant that a base oil is, or is derived from, a synthesis product of a Fischer- Tropsch process. A Fischer-Tropsch derived base oil may also be referred to as a GTL (Gas-To-Liquids) base oil. Suitable Fischer-Tropsch derived base oils that may be conveniently used as the base oil are those as for example disclosed in EP 0 776 959, EP 0 668 342, WO 97/21788, WO 00/15736, WO 00/14188, WO 00/14187, WO 00/14183, WO 00/14179, WO 00/08115, WO 99/41332, EP 1 029 029, WO 01/18156 and WO 01/57166.

[0017] Synthetic oils include hydrocarbon oils such as olefin oligomers (including polyalphaolefin base oils; PAOs), dibasic acid esters, polyol esters, polyalkylene glycols (PAGs), alkyl naphthalenes and dewaxed waxy isomerates. Synthetic hydrocarbon base oils sold by the Shell Group under the designation "Shell XHVI" (trade mark) may be conveniently used.

[0018] Poly-alpha olefin base oils (PAOs) and their manufacture are well known in the art. Suitable poly-alpha olefin base oils that may be used include those derived from linear C₂ to C32, preferably C₆ to Ci₆, alpha olefins. Particularly preferred feedstocks for said poly-alpha olefins are 1-octene, 1-decene, 1-dodecene and 1-tetradecene.

[0019] Preferably, the base oil comprises mineral oils and/or synthetic oils which contain more than 80% wt. of saturates, preferably more than 90% wt., as measured according to ASTM D2007.

[0020] It is further preferred that the base oil contains less than 1.0 wt. %, preferably less than 0.03 wt. % of sulfur, calculated as elemental sulfur and measured according to ASTM D2622, ASTM D4294, ASTM D4927 or ASTM D3120.

[0021] Preferably, the viscosity index of the base oil is more than 80, more preferably more than 120, as measured according to ASTM D2270.

[0022] Preferably, the base oil preferably has a kinematic viscosity at 100°C that is in the range of 3.8 mm²/s to 16.3 mm²/s (according to ASTM D445). In some embodiments, the base oil has a kinematic viscosity at 100°C of between 5.6 and 12.5 mm²/s.

[0023] The total amount of base oil incorporated in the lubricant compositions is preferably in an amount in the range of from 60 to 99 wt. %, more preferably in an amount in the range of from 65 to 90 wt. % and most preferably in an amount in the range of from 75 to 88 wt. %, with respect to the total weight of the lubricant composition.

[0024] Typically the lubricating compositions of the present invention would be utilized in, but not necessarily limited to, SAE J300 viscosity grades OW-20, 0W-30, 0W- 40, 5W-20, 5W-30 and 5W-40 as these are the grades which target fuel economy. As new SAE J300 viscosity grades are published, with lower viscosities than the current OW-20, the present invention would also be very much applicable to these new viscosity lower grades. It is conceivable that the present invention could also be used with higher viscosity grades.

[0025] The lubricating composition according to the present invention preferably has a Noack volatility (according to ASTM D 5800) of below 15 wt.%. Typically, the Noack volatility (according to ASTM D 5800) of the composition is between 1 and 15 wt. , preferably below 14.6 wt. and more preferably below 14.0 wt. .

B. Dialkyl Sulfosuccinate Salt

[0026] In addition to the base oil, the lubricating compositions of the present invention further comprise a dialkyl sulfosuccinate salt having the general formula:

wherein R and R' are independently selected from a linear or branched alkyl group containing 1 to 100 carbon atoms, Ri and R₂ are independently selected from the group consisting of hydrogen and a linear or branched alkyl group containing 1 to 100 carbon atoms, R₃ is selected from the group consisting of hydrogen, a linear or branched alkyl group containing 1 to 100 carbon atoms, and SO₃ X^"1", and X⁺ is selected from the group consisting of an alkali metal (e.g., lithium, sodium, potassium, rubidium, cesium), calcium, magnesium and ammonium. In some embodiments, R, R', Ri, R₂ and R₃ are independently selected from a linear or branched alkyl group containing 1 to 50 carbon atoms. In other embodiments, R, R', Ri, R₂ and R₃ are independently selected from a linear or branched alkyl group containing 1 to 20 carbon atoms.

[0027] In some embodiments, a dialkyl sulfosuccinate salt suitable for use in the present invention is a dioctyl sulfosuccinate salt, preferably, sodium dioctyl sulfosuccinate.

[0028] In one particular aspect of the present invention, the dialkyl sulfosuccinate salt may be provided in combination with a diluent. Examples of suitable diluents may include, but are not limited to, light petroleum distillate, various conventional mineral oils, synthetic oils, as well as any base oil which belongs to Group I, Group II, Group III, Group IV, Group V and so on of the API (American Petroleum Institute) base oil categories.

[0029] The total amount of dialkyl sulfosuccinate salt incorporated in the lubricant compositions is preferably in an amount of from 0.01 wt to 6 wt , more preferably from 0.05 wt to 3 wt , and even more preferably from 0.1 wt to 1 wt , by weight of the total lubricating composition.

[0030] Suitable dialkyl sulfosuccinate salts are commercially available and in one embodiment, may be prepared in accordance with the reaction shown below by esterifying succinic anhydride with an alcohol to form the dialkyl ester, followed by reacting the dialkyl ester with a metal metabisulfite (e.g., sodium metabisulfite).

An example of a commercially available dialkyl sulfosuccinate salt component suitable for use herein is available from Cytec under the tradename Aerosol^® OT-S & OT-100.

C. Other Additives

[0031] The lubricating composition according to the present invention may further comprise one or more additives such as anti-oxidants, anti-wear additives, dispersants, detergents, overbased detergents, extreme pressure additives, friction modifiers, viscosity index improvers, pour point depressants, metal passivators, corrosion inhibitors, demulsifiers, anti-foam agents, seal compatibility agents and additive diluent base oils, etc.

[0032] As the person skilled in the art is familiar with the above and other additives, these are not further discussed here in detail. Specific examples of such additives are described in for example Kirk-Othmer Encyclopedia of Chemical Technology, third edition, volume 14, pages 477-526.

[0033] Anti-oxidants that may be conveniently used include phenyl- naphthylamines (such as "IRGANOX^® L-06" available from Ciba Specialty Chemicals) and diphenylamines (such as "IRGANOX^® L-57" available from Ciba Specialty Chemicals) as e.g. disclosed in WO 2007/045629 and EP 1 058 720 Bl, phenolic antioxidants, etc. The teaching of WO 2007/045629 and EP 1 058 720 Bl is hereby incorporated by reference.

[0034] Anti-wear additives that may be conveniently used include zinc-containing compounds such as zinc dithiophosphate compounds selected from zinc dialkyl-, diaryl- and/or alkylaryl- dithiophosphates, molybdenum-containing compounds, boron-containing compounds and ashless anti-wear additives such as substituted or unsubstituted thiophosphoric acids, and salts thereof. Examples of such molybdenum-containing compounds may conveniently include molybdenum dithiocarbamates, trinuclear molybdenum compounds, for example as described in WO 98/26030, sulphides of molybdenum and molybdenum dithiophosphate.

[0035] Boron-containing compounds that may be conveniently used include borate esters, borated fatty amines, borated epoxides, alkali metal (or mixed alkali metal or alkaline earth metal) borates and borated overbased metal salts.

[0036] The dispersant used is preferably an ashless dispersant. Suitable examples of ashless dispersants are polybutylene succinimide polyamines and Mannich base type dispersants.

[0037] The detergent used is preferably an overbased detergent or detergent mixture containing e.g. salicylate, sulphonate and/or phenate-type detergents.

[0038] Examples of viscosity index improvers which may conveniently be used in the lubricating composition of the present invention include the styrene -butadiene stellate copolymers, styrene-isoprene stellate copolymers and the polymethacrylate copolymer and ethylene-propylene copolymers (also known as olefin copolymers) of the crystalline and non-crystalline type. Dispersant-viscosity index improvers may be used in the lubricating composition of the present invention. However, preferably the composition according to the present invention contains less than 1.0 wt. , preferably less than 0.5 wt. , of a Viscosity Index improver concentrate (i.e. VI improver plus "carrier oil" or "diluent"), based on the total weight of the composition. Most preferably, the composition is free of Viscosity Index improver concentrate. The term "Viscosity Modifier" as used hereafter (such as in Table 2) is meant to be the same as the above-mentioned term "Viscosity Index improver concentrate".

[0039] Preferably, the composition contains at least 0.1 wt.% of a pour point depressant. As an example, alkylated naphthalene and phenolic polymers, polymethacrylates, maleate/fumarate copolymer esters may be conveniently used as effective pour point depressants. Preferably not more than 0.3 wt.% of the pour point depressant is used.

[0040] Furthermore, compounds such as alkenyl succinic acid or ester moieties thereof, benzotriazole-based compounds and thiodiazole -based compounds may be conveniently used in the lubricating composition of the present invention as corrosion inhibitors.

[0041] Compounds such as polysiloxanes, dimethyl polycyclohexane and polyacrylates may be conveniently used in the lubricating composition of the present invention as defoaming agents.

[0042] Compounds which may be conveniently used in the lubricating composition of the present invention as seal fix or seal compatibility agents include, for example, commercially available aromatic esters.

[0043] The above-mentioned additives are typically present in an amount in the range of from 0.01 to 35.0 wt.%, based on the total weight of the lubricating composition, preferably in an amount in the range of from 0.05 to 25.0 wt.%, more preferably from 1.0 to 20.0 wt.%, based on the total weight of the lubricating composition.

[0044] The lubricant compositions may be conveniently prepared using conventional formulation techniques by admixing a base oil with a dialkyl sulfosuccinate salt and, if desired, one or more additives.

[0045] The lubricating compositions according to the present invention may be so- called "low SAPS" (SAPS = sulphated ash, phosphorus and sulphur), "mid SAPS" or "regular SAPS" formulations.

[0046] For Passenger Car Motor Oil (PCMO) engine oils the above ranges mean:

- a sulphated ash content (according to ASTM D 874) of up to 0.5 wt.%, up to 0.8 wt.% and up to 1.5 wt.%, respectively;

- a phosphorus content (according to ASTM D 5185) of up to 0.05 wt.%, up to 0.08 wt.% and typically up to 0.1 wt.%, respectively; and

- a sulphur content (according to ASTM D 5185) of up to 0.2 wt.%, up to 0.3 wt.% and typically up to 0.5 wt.%, respectively.

[0047] For Heavy Duty Diesel Engine Oils the above ranges mean:

- a sulphated ash content (according to ASTM D 874) of up to 1 wt.%, up to 1 wt.% and up to 2 wt.%, respectively;

- a phosphorus content (according to ASTM D 5185) of up to 0.08 wt.% (low SAPS) and up to 0.12 wt.% (mid SAPS), respectively; and

- a sulphur content (according to ASTM D 5185) of up to 0.3 wt.% (low SAPS) and up to 0.4 wt.% (mid SAPS), respectively.

[0048] In another aspect, the present invention provides the use of a lubricating composition according to the present invention as an engine oil in the crankcase of an engine, in order to improve sustained fuel economy properties while also improving dispersancy and piston cleanliness properties. The engine oil may include a heavy duty diesel engine oil, a passenger car motor engine oil, as well as other types of engine oils. [0049] In another aspect, the present invention provides methods that comprise introducing a lubricant composition comprising a dialkyl sulfosuccinate salt into a crankcase of an engine.

[0050] The present invention is described below with reference to the following Examples, which are not intended to limit the scope of the present invention in any way.

EXAMPLES

[0051] Various engine oils for use in a crankcase engine were formulated.

[0052] Table 1 indicates the properties for the base oils used.

[0053] "Base oil 1" was a Fischer- Tropsch derived base oil ("GTL 4") having a kinematic viscosity at 100°C (ASTM D445) of approx. 4 cSt (mmV¹). This GTL 4 base oil may be conveniently manufactured by the process described in e.g. WO 02/070631, the teaching of which is hereby incorporated by reference.

[0054] "Base oil 2" was a Fischer- Tropsch derived base oil ("GTL 8") having a kinematic viscosity at 100°C (ASTM D445) of approx. 8 cSt (mmV¹). This GTL 8 base oil may be conveniently manufactured by the process described in e.g. WO 02/070631, the teaching of which is hereby incorporated by reference.

[0055] "Base oil 3" was a commercially available Group III base oil having a kinematic viscosity at 100°C (ASTM D445) of 4.2 cSt (average value). Base oil 3 is commercially available from e.g. SK Energy (Ulsan, South Korea) (under the trade designation "Yubase 4").

[0056] "Base oil 4" was a commercially available Group III base oil having a kinematic viscosity at 100°C (ASTM D445) of 6.5 cSt (average value). Base oil 4 is commercially available from e.g. SK Energy (Ulsan, South Korea) (under the trade designation "Yubase 6").

TABLE 1

According to ASTM D 445. Average figures quoted.

2According to ASTM D 2270. Minimum values quoted.

3According to ASTM D 5950. Maximum values quoted.

According to CEC L-40-A-93 / ASTM D 5800. Maximum values quoted.

[0057] Table 2 indicates the composition and properties of the fully formulated engine oil formulations that were tested; the amounts of the components are given in wt.%, based on the total weight of the fully formulated formulations.

[0058] All tested engine oil formulations contained a combination of a base oil, an additive package, a pour point depressant, and a viscosity modifier. Examples 1 and 2 further contained sodium dioctyl sulfosuccinate. Example 3 and Comparative Example 3 further contained an additive booster package.

[0059] Additive packages 1 and 2 were so-called "mid SAPS" (medium sulphated ash, phosphorus and sulphur (e.g., SAPS level of approximately 1 wt%) formulations. Both additive packages contained a combination of additives including anti-oxidants, a zinc-based anti-wear additive, an ashless dispersant, an overbased detergent mixture and an anti-foaming agent. The additive booster package contained an ashless dispersant.

[0060] The dialkyl sulfosuccinate salt was a commercially available sodium dioctyl sulfosuccinate available from Cytec under the tradename "Aerosol OT-S" & "Aerosol OT- 100".

[0061] The viscosity modifier was a conventional styrene-hydrogenated isoprene co-polymer viscosity modifier concentrate, commercially available from Infineum under the trade designation "SV 277".

[0062] The compositions of the Examples and the Comparative Examples were obtained by mixing the base oils with the other components, using conventional lubricant blending procedures.

[0063] In order to demonstrate the propensity of the lubricating compositions of the present invention to form deposits when subjected to high temperatures (thermal stability) the examples and comparative examples were subjected to the Hot Tube Test method, as described in US Patent Publication No. 2013/0230926. In the Hot Tube Test Method, the test sample is held at a "Sump Temperature" and periodically the sample is extracted by a glass tube which is held at a "Piston Temperature", and then returned to the Sump. Thus a thin film of the test sample is held at the piston temperature and periodically washed and renewed by sample from the sump. After several hours of this operation, a deposit of thermally degraded oil forms on the inside wall of the glass tube, and the extent to which this occurs can be correlated with piston cleanliness in the sequence IIIG engine test. The results of these tests are shown in Table 2.

TABLE 2

'According to ASTM D 445

According to ASTM D 4683

[0064] The results in Table 2 demonstrate that the lubricating compositions of the present invention surprisingly exhibit improved piston cleanliness and reduced high temperature deposit formation.

[0065] In order to demonstrate the phosphorous volatility of the compositions of the present invention, phosphorous volatility measurements were performed on Comparative Example 1 and Example 1 according to the SAVLAB PEI test. The results of these tests are shown in Table 3.

[0066] In order to demonstrate the propensity of the lubricating compositions of the present invention to form deposits when subjected to high temperatures, measurements were performed on Comparative Example 1 and Example 1 according to the industry standard TEOST MHT test (according to ASTM D 7097) and TEOST 33C test (ASTM D 6335). The results of these tests are shown in Table 3.

[0067] In order to demonstrate the copper corrosion properties of the lubricating compositions of the present invention, measurements were performed on Comparative Example 1 and Example 1 in accordance with ASTM D 130. The results of these tests are shown in Table 3.

[0068] In order to demonstrate the corrosion properties of the lubricating compositions of the present invention, measurements were performed on Comparative Example 1 and Example 1 in accordance with ASTM D 5968. The results of these tests are shown in Table 3.

[0069] In order to demonstrate the high temperature corrosion properties of the lubricating compositions of the present invention, measurements were performed on Comparative Example 1 and Example 1 in accordance with ASTM D 6594. The results of these tests are shown in Table 3.

TABLE 3

'According to ASTM D 7097 According to ASTM D 6335 According to ASTM D 130

According to ASTM D 5968 According to ASTM D 6594

[0070] As evident from the results shown in Table 3, the inclusion of 1 wt. Aerosol OT-S does not substantially change the phosphorous volatility of the inventive lubricant compositions, significantly improves the performance of TEOST MHT test, does not substantially change the total deposits in TEOST 33C test, does not substantially change most of the corrosion properties of the inventive lubricant compositions, with the exception of the corrosion performance of both copper and lead metals in the high temperature test, which is improved.

[0071] In order to demonstrate the fluorelastomer compatibility of the lubricating compositions of the present invention, measurements were performed in accordance with VW PV3334 on 1 wt.% Aerosol OT-S blended as top-treats into a conventional API "SN" quality fully formulated engine lubricant. The result of this test is shown in Table 4.

TABLE 4

[0072] As evident from this data, the inclusion of 1 wt.% Aerosol OT-S in the conventional API "SN" quality fully formulated engine lubricant passed fluoroelastomer compatibility testing in accordance with VW PV3334.

[0073] In order to demonstrate the elastomer compatibility of the lubricating compositions of the present invention, measurements were performed in accordance with Daimler VDA 675 301 on 1 wt.% Aerosol OT-S blended as top-treats into a conventional API "SN" quality fully formulated engine lubricant. The result of this test is shown in Table 5.

TABLE 5

[0074] As evident from this data, the inclusion of 1 wt.% Aerosol OT-S in the conventional API "SN" quality fully formulated engine lubricant passed all elastomer compatibility testing in accordance with VDA 675 301.

[0075] Therefore, the present invention is well adapted to attain the ends and advantages mentioned as well as those that are inherent therein. The particular embodiments disclosed above are illustrative only, as the present invention may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. Furthermore, no limitations are intended to the details of construction or design herein shown, other than as described in the claims below. It is therefore evident that the particular illustrative embodiments disclosed above may be altered or modified and all such variations are considered within the scope and spirit of the present invention. While compositions and methods are described in terms of "comprising," "containing," or "including" various components or steps, the compositions and methods can also "consist essentially of or "consist of the various components and steps. All numbers and ranges disclosed above may vary by some amount. Whenever a numerical range with a lower limit and an upper limit is disclosed, any number and any included range falling within the range is specifically disclosed. In particular, every range of values (of the form, "from about a to about b," or, equivalently, "from approximately a to b," or, equivalently, "from approximately a-b") disclosed herein is to be understood to set forth every number and range encompassed within the broader range of values. Also, the terms in the claims have their plain, ordinary meaning unless otherwise explicitly and clearly defined by the patentee. Moreover, the indefinite articles "a" or "an," as used in the claims, are defined herein to mean one or more than one of the element that it introduces. If there is any conflict in the usages of a word or term in this specification and one or more patent or other documents that may be incorporated herein by reference, the definitions that are consistent with this specification should be adopted.

Claims

C L A I M S

1. A method comprising:

introducing a lubricant composition comprising a base oil and a dialkyl

sulfosuccinate salt into a crankcase of an engine.

2. The method of claim 1 wherein the dialkyl sulfosuccinate salt has the general formula:

wherein R and R' are independently selected from a linear or branched alkyl group containing 1 to 100 carbon atoms, Ri and R₂ are independently selected from the group consisting of hydrogen and a linear or branched alkyl group containing 1 to 100 carbon atoms, R3 is selected from the group consisting of hydrogen, a linear or branched alkyl group containing 1 to 100 carbon atoms, and SO₃ X^"1", and X⁺ is selected from the group consisting of an alkali metal, calcium, magnesium and ammonium.

3. The method of claim 2 wherein the alkali metal is selected from the group consisting of lithium, sodium, potassium, rubidium, and cesium.

4. The method of claim 1 wherein the dialkyl sulfosuccinate salt is present in the lubricant composition in an amount of from 0.01 wt to 6 wt .

5. The method of claim 1 wherein the dialkyl sulfosuccinate salt is sodium dioctyl sulfosuccinate.

6. A lubricating composition for use in the crankcase of an engine comprising a base oil; and a dialkyl sulfosuccinate salt.

7. The lubricating composition of claim 6 wherein the dialkyl sulfosuccinate salt has the general formula:

wherein R and R' are independently selected from a linear or branched alkyl group containing 1 to 100 carbon atoms, R] and R₂ are independently selected from the group consisting of hydrogen and a linear or branched alkyl group containing 1 to 100 carbon atoms, R₃ is selected from the group consisting of hydrogen, a linear or branched alkyl group containing 1 to 100 carbon atoms, and SO₃ X^"1", and X⁺ is selected from the group consisting of an alkali metal, calcium, magnesium and ammonium.

8. The lubricating composition of claim 7 wherein the alkali metal is selected from the group consisting of lithium, sodium, potassium, rubidium, and cesium.

9. The lubricating composition of claim 6 wherein the dialkyl sulfosuccinate salt is present in the lubricant composition in an amount of from 0.01 wt to 6 wt .

10. The lubricating composition of claim 6 wherein the dialkyl sulfosuccinate salt is sodium dioctyl sulfosuccinate.

11. Use of a lubricating composition comprising a base oil and a dialkyl sulfosuccinate salt in the crankcase of an engine, in order to improve sustained fuel economy properties while obtaining improved piston cleanliness properties.

12. Use of a lubricating composition comprising a base oil and a dialkyl sulfosuccinate salt in the crankcase of an engine, in order to minimize the formation of engine deposits.