Patent Description:
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 CO<NUM> emissions reductions targets. Therefore, any incremental improvement in fuel economy (FE) is of great importance in the automotive sector. It is known that by reducing the friction and wear properties of a gasoline fuel composition, improvements in fuel economy performance in a spark ignition engine can be obtained.

<CIT> discloses the use of a complex ester to reduce fuel consumption. <CIT> discloses functional fluids for internal combustion engines comprising an alkanol amine derivative which provides improvements in lubricity of the fluid.

It has now surprisingly been found that the use of a selected amine-based deposit control additive (DCA) in combination with a selected complex ester in a gasoline fuel composition can provide a synergistic reduction in engine wear.

According to the present invention there is provided the use as defined in attached claim <NUM>, namely the use of (a) an amino-based deposit control additive; and (b) a complex ester obtainable by an esterification reaction between (A) at least one aliphatic linear or branched C2 to C12 dicarboxylic acid, (B) at least one aliphatic linear or branched polyhydroxy alcohol with <NUM> to <NUM> hydroxy groups and (C) as a chain stopping agent (C1) at least one aliphatic linear or branched C1-C30 monocarboxylic acid in case of an excess of component (B), or (C2) at least one aliphatic linear or branched monobasic C1-C30 alcohol in case of an excess of component (A);
in a gasoline fuel composition for the purpose of providing a synergistic reduction in engine wear in a spark ignition internal combustion engine fuelled with said gasoline fuel composition.

Disclosed is also the use of (a) an amino-based deposit control additive ; and (b) a complex ester obtainable by an esterification reaction between (A) at least one aliphatic linear or branched C2 to C12 dicarboxylic acid, (B) at least one aliphatic linear or branched polyhydroxy alcohol with <NUM> to <NUM> hydroxy groups and (C) as a chain stopping agent (C1) at least one aliphatic linear or branched C1-C30 monocarboxylic acid in case of an excess of component (B), or (C2) at least one aliphatic linear or branched monobasic C1-C30 alcohol in case of an excess of component (A);
in a gasoline fuel composition for the purpose of providing a synergistic reduction in friction in a spark ignition internal combustion engine fuelled with said gasoline fuel composition.

Further disclosed is a method for providing a synergistic reduction in engine wear in a spark ignition internal combustion engine, said method comprising fuelling an internal combustion engine with a gasoline fuel composition comprising:.

Also disclosed is a method for providing a synergistic reduction in friction in a spark ignition internal combustion engine, said method comprising fuelling an internal combustion engine with a gasoline fuel composition comprising:.

The gasoline fuel composition herein comprises a base fuel suitable for use in a spark ignition internal combustion engine, an amino-based deposit control additive and a complex ester. The base fuel suitable for use in a spark ignition internal combustion engine is a gasoline base fuel, and therefore the fuel composition herein is a gasoline fuel composition.

According to the present invention, there is provided a use for providing a synergistic reduction in engine wear. As used herein the term 'synergistic reduction in engine wear' means that the reduction in engine wear obtained with the fuel composition comprising a combination of the amino-based deposit control additive and the complex ester as described herein is greater than the simple sum of the engine wear reduction obtained with an analogous fuel formulation containing the amino-based deposit control additive alone (i.e. without the complex ester) and the engine wear reduction obtained with an analogous fuel formulation containing the complex ester alone (i.e. without the amino-based deposit control additive). In other words, the reduction in engine wear obtained via the uses of the present invention are synergistic rather than additive. In the context of this aspect of the invention, the term "reduction' may for instance be <NUM>% or more, preferably <NUM>% or more, more preferably <NUM>% or more, even more preferably <NUM>% or more, especially <NUM>% or more, more especially <NUM>% or more and even more especially <NUM>% or more of the engine wear provided by an analogous fuel formulation containing either an amino-based deposit control additive or a complex ester in accordance with the present invention. The reduction in engine wear may even be as high as <NUM>% of the engine wear provided by an analogous fuel formulation containing either an amino-based deposit control additive or a complex ester.

As used herein, the term 'synergistic reduction in friction' means that the friction reduction obtained with the fuel composition comprising a combination of the amino-based deposit control additive and the complex ester as described herein is greater than the simple sum of the friction reduction obtained with an analogous fuel formulation containing the amino-based deposit control additive alone (i.e. without the complex ester) and the friction reduction obtained with an analogous fuel formulation containing the complex ester alone (i.e. without the amino-based deposit control additive). In other words, the reduction in friction is synergistic rather than additive. In this context, the term "reduction' may for instance be <NUM>% or more, preferably <NUM>% or more, more preferably <NUM>% or more, even more preferably <NUM>% or more, especially <NUM>% or more, more especially <NUM>% or more and even more especially <NUM>% or more of the friction provided by an analogous fuel formulation containing either an amino-based deposit control additive or a complex ester to it The reduction in friction may even be as high as <NUM>% of the friction provided by an analogous fuel formulation containing either an amino-based deposit control additive or a complex ester.

A first component for use herein is an amino-based deposit control additive. As used herein, the term 'Deposit Control Additive' is used to refer a component which is also known in the art as a detergent. The amino-based deposit control additive typically has at least one hydrophobic hydrocarbon radical having a number-average molecular weight (Mn) of from <NUM> to <NUM><NUM> and at least one polar moiety selected from a mono- or polyamino group having up to <NUM> nitrogen atoms, of which at least one nitrogen atom has basic properties.

The hydrophobic hydrocarbon radical in the above amino-based deposit control additives, which ensures the adequate solubility in the base fluid, has a number-average molecular weight (Mn) of from <NUM> to <NUM><NUM>, especially from <NUM> to <NUM><NUM>, in particular from <NUM> to <NUM>. Typical hydrophobic hydrocarbon radicals, especially in conjunction with the polar moiety, include polyalkenes (polyolefins), such as the polypropenyl, polybutenyl and polyisobutenyl radicals each having Mn of from <NUM> to <NUM>, preferably from <NUM> to <NUM>, more preferably from <NUM> to <NUM>, and especially from <NUM> to <NUM>. A preferred hydrophobic hydrocarbon radical is a polyisobutenyl radical.

According to the invention, the amino-based deposit control additive is an aliphatic hydrocarbyl-substituted amine having at least one basic nitrogen atom wherein the hydrocarbyl group has a number average molecular weight of about <NUM> to <NUM>,<NUM>.

Non-limiting examples of the amino-based deposit control additives include the following:
Additives comprising mono- or polyamino groups (A1) are preferably polyalkenemono- or polyalkenepolyamines based on polypropene or conventional (i.e. having predominantly internal double bonds) polybutene or polyisobutene having Mn of from <NUM> to <NUM>. When polybutene or polyisobutene having predominantly internal double bonds (usually in the beta and gamma position) are used as starting materials in the preparation of the additives, a possible preparative route is by chlorination and subsequent amination or by oxidation of the double bond with air or ozone to give the carbonyl or carboxyl compound and subsequent amination under reductive (hydrogenating) conditions. The amines used here for the amination may be, for example, ammonia, monoamines or polyamines, such as dimethylaminopropylamine, ethylenediamine, diethylenetriamine, triethylenetetramine or tetraethylenepentamine. Corresponding additives based on polypropene are described in particular in <CIT>.

Further preferred additives comprising monoamino groups are the hydrogenation products of the reaction products of polyisobutenes having an average degree of polymerization of from <NUM> to <NUM>, with nitrogen oxides or mixtures of nitrogen oxides and oxygen, as described in particular in <CIT>.

Further preferred additives comprising monoamino groups are the compounds obtainable from polyisobutene epoxides by reaction with amines and subsequent dehydration and reduction of the amino alcohols, as described in particular in <CIT>.

A preferred amino-based deposit control additive for use herein is a polyisobutenyl amine. An example of a commercially available polyisobutenyl amine deposit control additive is that commercially available from BASF under the tradename Kerocom PIBA03.

The amino-based deposit control additive is present in the fuel composition at a level in the range from 50ppm to 2000ppm, more preferably from 90ppm to 1500ppm, even more preferably from 150ppm to 1000ppm, and especially from <NUM> ppm to <NUM> ppm, by weight of the total fuel composition.

In an especially preferred embodiment herein, the amino-based deposit control additive is present in the fuel composition at a level in the range from <NUM> ppm to <NUM> ppm, by weight of the total fuel composition.

A second essential component herein is a complex ester. The complex ester for use herein is obtainable by an esterification reaction between (A) at least one aliphatic linear or branched C2 to C12 dicarboxylic acid, (B) at least one aliphatic linear or branched polyhydroxy alcohol with <NUM> to <NUM> hydroxy groups and (C) as a chain stopping agent (C1) at least one aliphatic linear or branched C1-C30 monocarboxylic acid in case of an excess of component (B), or (C2) at least one aliphatic linear or branched monobasic C1-C30 alcohol in case of an excess of component (A).

The aliphatic dicarboxylic acids of component (A) may be branched or preferably linear; they may be unsaturated or preferably saturated. Typical examples for component (A) are ethanedioic acid (oxalic acid), propanedioic acid (malonic acid), butanedioic acid (succinic acid), (Z)-butenedioic acid (maleic acid), (E)-butenedioic acid (fumaric acid), pentadioic acid (glutaric acid), pent-<NUM>-enedioic acid (glutaconic acid), hexanedioic acid (adipic acid), heptanedioic acid (pimelic acid), octanedioic acid (suberic acid), nonanedioic acid (azelaic acid), decanedioic acid (sebacic acid), undecanedioic acid, dodecanedioic acid, dodec-<NUM>-enedioic acid (traumatic acid) and (2E,4E)-hexa-<NUM>,<NUM>-dienedioic acid (muconic acid). Mixtures of the above aliphatic dicarboxylic acids can also be used.

In a preferred embodiment, the at least one aliphatic dicarboxylic acid of component (A) is selected from aliphatic, linear C6-C10 dicarboxylic acids which are preferably saturated. Most preferred are adipic acid and sebacic acid.

In a particularly preferred embodiment herein, the at least one aliphatic dicarboxylic acid of component (A) is adipic acid.

The aliphatic polyhydroxy alcohols of component (B) may be branched or linear; they may be unsaturated or preferably saturated; they may contain from <NUM> to <NUM>, preferably from <NUM> to <NUM>, especially from <NUM> to <NUM> carbon atoms and preferably <NUM>, <NUM> or <NUM> hydroxyl groups. Typical examples for component (B) are trimethylolethane, trimethylol-propane, trimethylolbutane, sorbitol, glycerin and pentaerythritol. Mixtures of the above aliphatic polyhydroxy alcohols can also be used.

In a preferred embodiment, the at least one aliphatic polyhydroxy alcohol of component (B) is selected from glycerin, trimethylolpropane and pentaerythritol.

In another preferred embodiment, the at least one aliphatic polyhydroxy alcohol of component (B) is selected from trimethylolpropane and pentaerythritol.

In a particularly preferred embodiment herein, the at least one aliphatic polyhydroxy alcohol of component (B) is trimethylolpropane.

Depending whether component (B) is used for the esterification reaction in an excess compared with component (A), resulting in remaining free hydroxyl groups, or component (A) is used for the esterification reaction in an excess compared with component (B), resulting in remaining free carboxylic groups, chain stopping agent (C1) or (C2) is used for the synthesis of the complex ester mentioned. Carboxylic ester component (C1) will transform remaining free hydroxyl groups into additional carboxylic ester groups. Monobasic alcohol component (C2) will transform remaining free carboxylic groups into additional carboxylic ester groups.

The aliphatic monocarboxylic acids of component (C1) may be branched or linear, they may be unsaturated or preferably saturated. Typical examples for component (C1) are formic acid, acetic acid, propionic acid, <NUM>,<NUM>-dimethyl propionic acid (neopentanoic acid), hexanoic acid, octanoic acid (caprylic acid), <NUM>-ethylhexanoic acid, <NUM>,<NUM>,<NUM>-trimethyl hexanoic acid, nonanoic acid, decanoic acid (capric acid), undecanoic acid, dodecanoic acid (lauric acid), tridecanoic acid, tetradecanoic acid (myristic acid), hexadecenoic acid (palmitic acid), octadecanoic acid (stearic acid), isostearic acid, oleic acid, linoleic acid, linoelaidic acid, erucic acid, arachidic acid, behenic acid, lignoceric acid and cerotic acid. The above monocarboxylic acids, including the so-called fatty acids, may be of synthetic or of natural origin. Mixtures of the above aliphatic monocarboxylic acids can also be used.

In a preferred embodiment, the at least one aliphatic monocarboxylic acid of component (C1) is selected from aliphatic linear or branched C8 to C18 monocarboxylic acids.

In a particularly preferred embodiment, the at least one aliphatic monocarboxylic acid of component (C1) is selected from aliphatic linear or branched C8 to C10 monocarboxylic acids.

The aliphatic monobasic alcohols of component (C2) may be branched or linear; they may be unsaturated, or preferably saturated. Typical examples for component (C2) are methanol, ethanol, n-propanol, iso-propanol, n-butanol, iso-butanol, sec-butanol, tert-butanol, n-pentanol, n-hexanol, n-heptanol, n-octanol, <NUM>-ethylhexanol, n-nonanol, <NUM>-propylheptanol, n-decanol, n-undecanol, n-dodecanol, n-tridecanol, iso-tridecanol, n-tetradecanol, iso-tetradecanol, n-hexadecanol, n-octadecanol, iso-octadecanol and n-eicosanol. Mixtures of the above monobasic alcohols can also be used. The said monobasic alcohols may have been alkoxylated by means of hydrocarbyl epoxides like ethylene oxide, propylene oxide and/or butylene oxide resulting in monocapped polyethers before being used as chain stopping agents for preparing the complex esters mentioned.

In a preferred embodiment, the at least one aliphatic monobasic alcohol of component (C2) is selected from linear or branched C8-C18 alkanols.

In one preferred embodiment of the present invention, the at least one aliphatic dicarboxylic acid of component (A) is selected from aliphatic, linear C6-C10 dicarboxylic acids which are preferably saturated, the at least one aliphatic polyhydroxy alcohol of component (B) is selected from glycerin, trimethylolpropane and pentaerythritol and the chain stopping agent (C) is at least one aliphatic monocarboxylic acid component (C1) selected from aliphatic linear or branched C8 to C18 monocarboxylic acids.

In a particularly preferred embodiment of the present invention, the at least one aliphatic dicarboxylic acid of component (A) is selected from adipic acid or sebacic acid, the at least one aliphatic polyhydroxy alcohol of component (B) is trimethylolpropane or pentaerythritol and the chain stopping agent (C) is an aliphatic monocarboxylic acid component (C1) selected form aliphatic linear or branched C8 to C18 monocarboxylic acids.

In an especially preferred embodiment of the present invention, the at least one aliphatic dicarboxylic acid of component (A) is selected from adipic acid, the at least one aliphatic polyhydroxy alcohol of component (B) is trimethylolpropane and the chain stopping agent (C) is an aliphatic monocarboxylic acid component (C1) selected form aliphatic linear or branched C8 to C10 monocarboxylic acids.

The synthesis of the complex ester is known in the art. Further details of the synthesis can be found in <CIT>. It can be prepared by mixing and reacting component (A) with (B) and subsequently reacting the intermediate ester formed by (A) and with component (C). As an alternative, it can also be prepared by mixing and reacting components (A), (B) and (C) simultaneously.

The complex ester mentioned is normally composed of at least <NUM> molecule units of component (A), at least <NUM> molecule units of component (B) and the corresponding number of molecule units of chain stopping agent (C), or of at least <NUM> molecule units of component (B), at least <NUM> molecule units of component (A) and the corresponding number of molecule units of chain stopping agent (C).

In a preferred embodiment, the complex ester mentioned is composed from <NUM> to <NUM> molecule units, especially from <NUM> to <NUM> molecule units of component (A) and from <NUM> to <NUM> molecule units, especially from <NUM> to <NUM> molecule units of component (B), component (B) being in excess compared with component (A), with remaining free hydroxyl groups of (B) being completely or partly capped with a corresponding number of molecule units of component (C1).

In another preferred embodiment, the complex ester mentioned is composed of from <NUM> to <NUM> molecule units, especially from <NUM> to <NUM> molecule units of component (A) and from <NUM> to <NUM> molecule units, especially from <NUM> to <NUM> molecule units of component (B), component (A) being in excess compared with component (B), with remaining free carboxyl groups of (A) being completely or partly capped with a corresponding number of molecule units of component (C2).

A typical complex ester useful for the instant invention is composed of <NUM> or <NUM> molecule units of component (A), especially of at least one aliphatic linear C6 to C10 dicarboxylic acid such as adipic acid and/or sebacic acid, or <NUM> or <NUM> molecule units of component (B), especially of glycerin, trimethylolpropane and/or pentaerythritol, and of <NUM> to <NUM> molecule units of component (C1), especially of at least one aliphatic linear or branched C8 to C18 monocarboxylic acid such as octanoic acid, <NUM>-ethylhexanoic acid, <NUM>,<NUM>,<NUM>-trimethyl hexanoic acid, nonanoic acid, decanoic acid and/or isostearic acid.

Particularly preferred complex esters for use herein are Examples <NUM> and <NUM> of <CIT>.

In one embodiment herein, the complex ester for use herein is Example <NUM> of <CIT>.

In another embodiment herein, the complex ester for use herein is Example <NUM> of <CIT>.

The complex ester mentioned is oil soluble, which means that, when mixed with mineral oils and/or fuels in a weight ratio of <NUM>:<NUM>, <NUM>:<NUM> and <NUM>:<NUM>, the complex ester does not show phase separation after standing for <NUM> hours at room temperature for at least two weight ratios our of the three weight ratios <NUM>:<NUM>, <NUM>:<NUM> and <NUM>:<NUM>.

Typically, the amount of this at least one complex ester in the gasoline fuel composition herein is <NUM> to <NUM> ppm by weight, more preferably from <NUM> to <NUM> ppm by weight, even more preferably from <NUM> to <NUM> ppm by weight and especially from <NUM> to <NUM> ppm by weight, for example <NUM> to <NUM> ppm by weight.

In one embodiment of the present invention, the amount of the at least one complex ester in the gasoline fuel composition herein is from <NUM> ppm to <NUM> ppm, by weight of the gasoline fuel composition.

In a preferred embodiment of the present invention, the amino-based deposit control additive is present in the fuel composition at a level in the range from <NUM> ppm to <NUM> ppm, by weight of the total fuel composition and the at least one complex ester is present in the fuel composition at a level in the range from <NUM> ppm to <NUM> ppm, by weight of the gasoline fuel composition.

In a particularly preferred embodiment of the present invention, the amino-based deposit control additive is present in the fuel composition at a level in the range from <NUM> ppm to <NUM> ppm, by weight of the total fuel composition and the at least one complex ester is present in the fuel composition at a level in the range from <NUM> ppm to <NUM> ppm, by weight of the gasoline fuel composition. According to the invention the weight ratio of the amino-based deposit control additive to the at least one complex ester is in the range from <NUM>:<NUM> to <NUM>:<NUM>.

The amino-based deposit control additive and the complex ester can be added to the gasoline base fuel either individually or in the form of fuel additive packages (also known as gasoline performance packages). Such packages are fuel additive concentrates and part of an additive blend. The additive blend is then added to a gasoline base fuel to produce a gasoline fuel composition.

The weight ratio of the amino-based deposit control additive to the complex ester is in the range from <NUM>:<NUM> to <NUM>:<NUM>, more preferably from <NUM>:<NUM> to <NUM>:<NUM>.

In one embodiment of the present invention, the weight ratio of the amino-based deposit control additive to the complex ester is in the range from <NUM>:<NUM> to <NUM>:<NUM>.

In another embodiment of the present invention, the weight ratio of the amino-based deposit control additive to the complex ester is in the range from <NUM>:<NUM> to <NUM>:<NUM>.

In the liquid fuel compositions if the base fuel used is a gasoline, then the gasoline may be any gasoline suitable for use in an internal combustion engine of the spark-ignition (petrol) type known in the art, including automotive engines as well as in other types of engine such as, for example, off road and aviation engines. The gasoline used as the base fuel in the liquid fuel composition may conveniently also be referred to as 'base gasoline'.

Gasolines typically comprise mixtures of hydrocarbons boiling in the range from <NUM> to <NUM> (EN-ISO <NUM>), the optimal ranges and distillation curves typically varying according to climate and season of the year. The hydrocarbons in a gasoline may be derived by any means known in the art, conveniently the hydrocarbons may be derived in any known manner from straight-run gasoline, synthetically-produced aromatic hydrocarbon mixtures, thermally or catalytically cracked hydrocarbons, hydro-cracked petroleum fractions, catalytically reformed hydrocarbons or mixtures of these.

The specific distillation curve, hydrocarbon composition, research octane number (RON) and motor octane number (MON) of the gasoline are not critical.

Conveniently, the research octane number (RON) of the gasoline may be at least <NUM>, for instance in the range of from <NUM> to <NUM>, preferably the RON of the gasoline will be at least <NUM>, for instance in the range of from <NUM> to <NUM>, more preferably the RON of the gasoline will be at least <NUM>, for instance in the range of from <NUM> to <NUM>, even more preferably the RON of the gasoline will be at least <NUM>, for instance in the range of from <NUM> to <NUM>, even more preferably the RON of the gasoline will be at least <NUM>, for instance in the range of from <NUM> to <NUM>, and most preferably the RON of the gasoline will be at least <NUM>, for instance in the range of from <NUM> to <NUM> (DIN EN ISO <NUM>) the motor octane number (MON) of the gasoline may conveniently be at least <NUM>, for instance in the range of from <NUM> to <NUM>, preferably the MON of the gasoline will be at least <NUM>, for instance in the range of from <NUM> to <NUM>, more preferably the MON of the gasoline will be at least <NUM>, for instance in the range of from <NUM> to <NUM>, most preferably the MON of the gasoline will be at least <NUM>, for instance in the range of from <NUM> to <NUM> (DIN EN ISO <NUM>).

Typically, gasolines comprise components selected from one or more of the following groups; saturated hydrocarbons, olefinic hydrocarbons, aromatic hydrocarbons, and oxygenated hydrocarbons. Conveniently, the gasoline may comprise a mixture of saturated hydrocarbons, olefinic hydrocarbons, aromatic hydrocarbons, and, optionally, oxygenated hydrocarbons.

Typically, the olefinic hydrocarbon content of the gasoline is in the range of from <NUM> to <NUM> percent by volume based on the gasoline (ASTM D1319); preferably, the olefinic hydrocarbon content of the gasoline is in the range of from <NUM> to <NUM> percent by volume based on the gasoline, more preferably, the olefinic hydrocarbon content of the gasoline is in the range of from <NUM> to <NUM> percent by volume based on the gasoline.

Typically, the aromatic hydrocarbon content of the gasoline is in the range of from <NUM> to <NUM> percent by volume based on the gasoline (ASTM D1319), for instance the aromatic hydrocarbon content of the gasoline is in the range of from <NUM> to <NUM> percent by volume based on the gasoline; preferably, the aromatic hydrocarbon content of the gasoline is in the range of from <NUM> to <NUM> percent by volume based on the gasoline, for instance the aromatic hydrocarbon content of the gasoline is in the range of from <NUM> to <NUM> percent by volume based on the gasoline.

The benzene content of the gasoline is at most <NUM> percent by volume, more preferably at most <NUM> percent by volume, especially at most <NUM> percent by volume based on the gasoline.

The gasoline preferably has a low or ultra low sulphur content, for instance at most <NUM> ppmw (parts per million by weight), preferably no more than <NUM> ppmw, more preferably no more than <NUM>, even more preferably no more than <NUM> and most preferably no more than even <NUM> ppmw.

The gasoline also preferably has a low total lead content, such as at most <NUM>/l, most preferably being lead free - having no lead compounds added thereto (i.e. unleaded).

When the gasoline comprises oxygenated hydrocarbons, at least a portion of non-oxygenated hydrocarbons will be substituted for oxygenated hydrocarbons. The oxygen content of the gasoline may be up to <NUM> percent by weight (EN <NUM>) (e.g. ethanol per se) based on the gasoline. For example, the oxygen content of the gasoline may be up to <NUM> percent by weight, preferably up to <NUM> percent by weight. Conveniently, the oxygenate concentration will have a minimum concentration selected from any one of <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> percent by weight, and a maximum concentration selected from any one of <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> percent by weight.

Examples of oxygenated hydrocarbons that may be incorporated into the gasoline include alcohols, ethers, esters, ketones, aldehydes, carboxylic acids and their derivatives, and oxygen containing heterocyclic compounds. Preferably, the oxygenated hydrocarbons that may be incorporated into the gasoline are selected from alcohols (such as methanol, ethanol, propanol, <NUM>-propanol, butanol, tert-butanol, iso-butanol and <NUM>-butanol), ethers (preferably ethers containing <NUM> or more carbon atoms per molecule, e.g., methyl tert-butyl ether and ethyl tert-butyl ether) and esters (preferably esters containing <NUM> or more carbon atoms per molecule); a particularly preferred oxygenated hydrocarbon is ethanol.

When oxygenated hydrocarbons are present in the gasoline, the amount of oxygenated hydrocarbons in the gasoline may vary over a wide range. For example, gasolines comprising a major proportion of oxygenated hydrocarbons are currently commercially available in countries such as Brazil and U. , e.g. ethanol per se and E85, as well as gasolines comprising a minor proportion of oxygenated hydrocarbons, e.g. E10 and E5. Therefore, the gasoline may contain up to <NUM> percent by volume oxygenated hydrocarbons. E100 fuels as used in Brazil are also included herein. Preferably, the amount of oxygenated hydrocarbons present in the gasoline is selected from one of the following amounts: up to <NUM> percent by volume; up to <NUM> percent by volume; up to <NUM> percent by volume; up to <NUM> percent by volume; up to <NUM> percent by volume; up to <NUM> percent by volume; and, up to <NUM> percent by volume, depending upon the desired final formulation of the gasoline. Conveniently, the gasoline may contain at least <NUM>, <NUM> or <NUM> percent by volume oxygenated hydrocarbons.

Examples of suitable gasolines include gasolines which have an olefinic hydrocarbon content of from <NUM> to <NUM> percent by volume (ASTM D1319), an oxygen content of from <NUM> to <NUM> percent by weight (EN <NUM>), an aromatic hydrocarbon content of from <NUM> to <NUM> percent by volume (ASTM D1319) and a benzene content of at most <NUM> percent by volume.

Also suitable for use herein are gasoline blending components which can be derived from a biological source. Examples of such gasoline blending components can be found in <CIT>, <CIT>, <CIT>, <CIT><CIT><CIT>, and <CIT>.

Whilst not critical to the present invention, the base gasoline or the gasoline composition may conveniently include one or more optional fuel additives, in addition to the essential amino-based deposit control additive and complex ester mentioned above. The concentration and nature of the optional fuel additive(s) that may be included in the base gasoline or the gasoline composition of the present invention is not critical. Non-limiting examples of suitable types of fuel additives that can be included in the base gasoline or the gasoline composition include anti-oxidants, corrosion inhibitors, deposit control additives/detergents other than the amino-based deposit control additive mentioned above, dehazers, antiknock additives, metal deactivators, valve-seat recession protectant compounds, dyes, solvents, carrier fluids, diluents and markers. Examples of suitable such additives are described generally in <CIT>.

Conveniently, the fuel additives can be blended with one or more solvents to form an additive concentrate, the additive concentrate can then be admixed with the base gasoline or the gasoline composition.

The (active matter) concentration of any optional additives present in the base gasoline or the gasoline composition is preferably up tc <NUM> percent by weight, more preferably in the range from <NUM> to <NUM> ppmw, advantageously in the range of from <NUM> to <NUM> ppmw, such as from <NUM> to <NUM> ppmw.

As stated above, the gasoline composition may also contain synthetic or mineral carrier oils and/or solvents.

The present invention will be further understood from the following examples. Unless otherwise stated, all amounts and concentrations disclosed in the examples are based on weight of the fully formulated fuel composition.

In the following examples, two friction modifiers were used. FM1 was a complex ester as disclosed in Example <NUM> of <CIT>. FM2 was a friction modifier (not having the complex ester structure mentioned hereinabove) commercially available from BASF under the tradename Kerocom FM38.

A Kerocom PIBA03 deposit control additive commercially available from BASF was used in the examples where indicated. The base fuel in Examples <NUM>-<NUM> was isooctane. Isooctane is a component of gasoline and was used as a reference base fuel in Examples <NUM>-<NUM> herein. The base fuel in Examples <NUM>-<NUM> was a standard E0 gasoline base fuel meeting the EN228 specification. Tables <NUM> and <NUM> shows the relative amounts (in ppm) of the various additives (FM1, FM2, PIBA Deposit Control Additive) in each fuel composition. The friction coefficient of each of the fuel compositions was measured using an HFRR method (using ASTM D6079 the test method) at <NUM>, <NUM> and <NUM>; <NUM> (Pmean = <NUM>. 55GPa); <NUM> mins; <NUM>; <NUM> stroke length. The friction results are shown in Table <NUM> below. The wear scar of each of the fuel compositions was also measured using the HFRR method. The wear scar results are shown in Table <NUM> below.

<FIG> are graphical representations of the results shown in Tables <NUM> and <NUM> above.

<FIG> is a graphical representation of the average friction coefficient at <NUM> for the fuels of Examples <NUM> to <NUM>.

<FIG> is a graphical representation of the wear scar average data at <NUM> for the fuels of Examples <NUM> to <NUM>.

<FIG> is a graphical representation of the friction coefficient data at <NUM> for the fuels of Examples <NUM>, <NUM> and <NUM>.

<FIG> is a graphical representation of the wear scar average data at <NUM> for the fuels of Examples <NUM>, <NUM> and <NUM>.

<FIG> is a graphical representation of the friction coefficient data at <NUM> for the fuels of Examples <NUM>,<NUM> and <NUM>.

<FIG> is a graphical representation of the average friction coefficient at <NUM> for the fuels of Examples <NUM>, <NUM>, <NUM> and <NUM>.

<FIG> is a graphical representation of the wear scar average data at <NUM> for the fuels of Examples <NUM>, <NUM>, <NUM> and <NUM>.

<FIG> is a graphical representation of the average friction coefficient at <NUM> for the fuels of Examples <NUM>,<NUM> and <NUM>.

<FIG> is a graphical representation of the average friction coefficient data at <NUM> for the fuels of Examples <NUM>-<NUM>.

<FIG> is a graphical representation of the wear scar data ay <NUM> for Examples <NUM>-<NUM>.

Claim 1:
Use of (a) an amino-based deposit control additive; and (b) a complex ester obtainable by an esterification reaction between (A) at least one aliphatic linear or branched C2 to C12 dicarboxylic acid, (B) at least one aliphatic linear or branched polyhydroxy alcohol with <NUM> to <NUM> hydroxy groups and (C) as a chain stopping agent (C1) at least one aliphatic linear or branched C1-C30 monocarboxylic acid in case of an excess of component (B), or (C2) at least one aliphatic linear or branched monobasic C1-C30 alcohol in case of an excess of component (A);
in a gasoline fuel composition for the purpose of providing a synergistic reduction in engine wear in a spark ignition internal combustion engine fuelled with said gasoline fuel composition;
wherein the amino-based deposit control additive is an aliphatic hydrocarbyl-substituted amine having at least one basic nitrogen atom wherein the hydrocarbyl group has a number average molecular weight of about <NUM> to <NUM>,<NUM>;
wherein the at least one complex ester is present in the gasoline fuel composition in an amount from 10ppmw to 5000ppmw, by weight of the gasoline fuel composition;
wherein the amino-based deposit control additive is present at a level from 50ppm to 2000ppm, by weight of the gasoline fuel composition;
and wherein the weight ratio of the amino-based deposit control additive to the complex ester is in the range from <NUM>:<NUM> to <NUM>:<NUM>.