WO1995012648A1

WO1995012648A1 - Compositions for control of induction system deposits in internal combustion engines

Info

Publication number: WO1995012648A1
Application number: PCT/GB1994/002364
Authority: WO
Inventors: Stanley Charles King; David Alan Cotter
Original assignee: Ethyl Petroleum Additives Limited
Priority date: 1993-11-01
Filing date: 1994-10-27
Publication date: 1995-05-11
Also published as: GB2283495A; GB9322513D0; AU7999194A; IL111418A0

Abstract

This invention relates to fuel additives and fuels containing such additives for minimizing induction system deposits in an internal combustion engine. The fuel additives comprise novel combinations of at least five specified components in specified proportions.

Description

COMPOSITIONS FOR CONTROL OF INDUCTION SYSTEM DEPOSITS IN INTERNAL COMBUSTION ENGINES

This invention relates to fuel additive concentrates, and liquid hydrocarbon fuels of enhanced performance char¬ acteristics.

An objective of this invention is to provide fuel ad- ditive concentrates and fuel compositions that can effec¬ tively minimize induction system deposits in internal com¬ bustion engines. Another objective is to provide additive combinations and fuels containing them that are capable of controlling octane requirement increase. A still further objective is to provide additive combinations and fuel com¬ positions that possess excellent low temperature handle- ability characteristics. Yet another objective is to pro¬ vide additive combinations that can be effectively used in fuels at relatively low concentrations while providing sig- nificant performance improvements. Still another objective is to provide fuel compositions which not only maintain in¬ duction system cleanliness but in addition, result in the formation of minimal combustion chamber deposits.

In accordance with this invention, it has been found possible to achieve the foregoing objectives by use of par¬ ticular additive components in particular relative propor¬ tions to each other in a hydrocarbonaceous fuel.

More particularly, an embodiment of this invention is a fuel additive concentrate which comprises at least the following components:

(a) at least one fuel-soluble Mannich base detergent/dis- persant;

SUBSTITUTESHEET(RULE2θ) (b) unhydrogenated poly-α-olefin oligomer having a vis¬ cosity in the range of 5 to 10 cSt at 100"C formed by oligomerization of C₈ to C₁₂ α-olefin;

(c) aromatic hydrocarbon boiling in the range of 160 to 300^βC and having a viscosity in the range of 1.2 to

2.0 cSt at 25°C;

(d) at least one fuel-soluble al anol having in the range of 5 to 13 carbon atoms per molecule; and

(e) at least one fuel-soluble sterically hindered alkyl- substituted mononuclear or non-fused ring polynuclear phenolic compound in which there are in the range of 10 to 20 carbon atoms per hydroxyl group and in which there is one and only one hydroxyl group attached to each aromatic nucleus; wherein the weight ratio of (e) : (a) is in the range of 0.05:1 to 0.5:1, the weight ratio of (d) : (a) is in the range of 0.1:1 to 2:1, the weight ratio of (c) : (a) is in the range of 0.1:1 to 3:1, and the weight ratio of (b) : (a) is in the range of 0.2:1 to 8:1. Preferred are composi- tions wherein the weight ratio of (e) : (a) is in the range of 0.05:1 to 0.25:1, the weight ratio of (d) : (a) is in the range of 0.1:1 to 1:1, the weight ratio of (c) : (a) is in the range of 1:1 to 2:1, and the weight ratio of (b) : (a) is in the range of 1:1 to 4:1. Especially preferred are con- centrates wherein the weight ratio of (e) : (a) is in the range of 0.08:1 to 0.12:1, the weight ratio of (d) : (a) is in the range of 0.1:1 to 0.5:1, the weight ratio of (c) : (a) is in the range of 1:1 to 2:1, and the weight ratio of (b) : (a) is in the range of 1.5:1 to 3:1. Any of the foregoing concentrates desirably contain at least one phenylene diamine antioxidant, or at least one fuel-soluble demulsifying agent, or at least one fuel-solu¬ ble corrosion inhibitor, or a combination of any two or all three of these additional components. Of various suitable poly-α-olefin oligomers for use in these various additive concentrates, the most preferred are oligomers of 1-decene having a viscosity in the range of 5.5 to 7.5 cSt at 100*C. Also the most preferred detergent/dispersant for such use is a Mannich base formed by reaction of an alkylphenol in which the alkyl group has a number average molecular weight in the range of 750 to 1200, polyalkylene polya ine and formaldehyde or a formaldehyde precursor.

Additional preferred concentrates of this invention are any of those referred to in the immediately preceding paragraph wherein the concentrate further comprises branch- ed chain alkane or alkene hydrocarbon having a number ave¬ rage molecular weight in the range of 750 to 1200 in an amount such that the weight ratio of said hydrocarbon to component (a) is in the range of 0.1:1 to 1:1, and espe¬ cially wherein the hydrocarbon is polypropene or hydro- genated polypropene and wherein said weight ratio of the hydrocarbon to component (a) is in the range of 0.1:1 to 0.5:1.

This invention also provides liquid fuel compositions containing the components of the foregoing additive con- centrates of this invention proportioned as above and pre¬ sent in the fuel in an amount at least sufficient to mini¬ mize induction system deposits in an internal combustion engine. While the additives of this invention are suitable for use in diesel fuels, the invention is particularly well adapted for improving performance of gasolines (petrol) . Optionally, the unleaded gasolines may also contain at least 5 volume % of a fuel-soluble dihydrocarbyl ether, typically an ether of the formula ROR' where R is methyl or ethyl and R' is tert-butyl or tert-amyl. When such ethers are utilized in motor gasolines, they are usually present in amounts of at least 10 volume percent.

Preferred gasolines are those containing no more than 3% by volume of olefins as determined by ASTM D1319. Most desirably the gasoline contains at least 50% by volume of saturates as determined by ASTM D1319 and contains less than 0.05 weight percent sulfur as determined by ASTM D3120.

Further embodiments involve the use of a plurality of additive components of this invention proportioned as de¬ scribed above in a hydrocarbonaceous fuel for an internal combustion engine (preferably gasoline) to control induc¬ tion system deposits. Most preferably, the foregoing addi¬ tive components proportioned as described above, are used in gasoline fuel compositions not only to control induction system deposits but additionally to minimize octane requir- e ent increase.

The foregoing and other advantages and embodiments of this invention will be apparent from the ensuing descrip¬ tion and appended claims.

A feature of this invention is that if the particular additive components are not employed, and if employed, are not employed in the proportions specified above, decidedly inferior results can be experienced.

Component a.. Any suitable fuel-soluble Mannich base detergent/dispersant can be used, such as for example the Mannich bases described in U.S. Pat. Nos. 3,948,619 and 3,994,698. However the preferred Mannich bases are as de- scribed in U.S. Pat. No. 4,231,759. For further details, one should refer to that document. Particularly preferred Mannich bases include those formed by reaction of an alkyl- phenol in which the alkyl group has a number average ole- cular weight in the range of 750 to 1200, polyalkylene polyamine and formaldehyde or a formaldehyde precursor. Mannich bases wherein the alkyl group of the alkylphenol is derived from polypropene having a number average molecular weight in the range of 800 to 950 and wherein the polyalky- lene polyamine is diethylene triamine are especially pre¬ ferred.

Component b.. In the practice of this invention the oligomer used must have a viscosity in the range of 5 to 10 cSt at 100^βC, and preferably the viscosity is in the range of 5.5 to 7.8 cSt at 100°C. Such oligomers can be produced by any known catalytic oligomerization procedure capable of producing products having these viscosity properties. One typical procedure for producing suitable poly-α-olefin oligomers is described in Published European Patent Appli- cation, Publication No. 0 526 129 (February 3, 1993). The literature describes other suitable procedures that can be used.

Component c) . Aromatic hydrocarbon solvents are available from a number of commercial sources. Small amounts (e.g., up to 5 volume %) of non-aromatic hydrocarbons can be present in the mixture provided they are neither olefinic or acetylenic in character. The important physical properties are the boiling range and viscosity of the mixture, and these properties have been described hereinabove. A preferred mixture of aromatic hydrocarbons boiling in the range of 175 to 220*c and having a 50% boiling temperature in the range of 185 to 195"C, said aromatic hydrocarbon containing from 75 to 80 volume percent of C₉ to C₁₂ alkylbenzenes, from 12 to 18 volume percent indans and tetrahydronaphthalenes, 6 to 9 volume percent naphthalenes and less than 1 volume percent of benzene as determined by gas chro atography.

Component d.. Fuel-soluble alkanols having in the range of 5 to 13 carbon atoms per molecule are available from various commercial sources. Preferably, the alkanol is a branched-chain alkanol having 7 to 10 carbon atoms in the molecule, and especially those in which the alkanol is a primary alkanol. The most preferred alkanol for use in the practice of this invention is 2-ethyl-l-hexanol.

Component e.. As pointed out above, this component is either a mononuclear monohydric phenol, or a non-fused ring polynuclear polyhydric phenol in which each aromatic nucle¬ us carries one and only one hydroxyl group. In addition, these phenolic compounds are fuel-soluble and are sterical- ly hindered alkyl-substituted phenolic compounds. In all cases, the phenolic compounds used have from 10 to 20 car¬ bon atoms per hydroxyl group. Preferred are mononuclear monohydric alkyl phenols having in the range of 10 to 18 carbon atoms per molecule. Especially effective are mix¬ tures of tertiary butylated phenols comprising at least 75 weight percent of 2,6-di-tert-butyl phenol. Examples of suitable phenolic compounds include 2-tert-butylphenol, 2,6-di-tert-butylphenol, 2, ,6-tri-tert-butylphenol, 4-me- thyl-2,6-di-tert-butylphenol, 2,4-dimethyl-6-tert-butyl- phenol, 2,2"-methylenebis(6-tert-butyl-4-methylphenol) , 2,2'-methylenebis(6-tert-butyl-4-ethylphenol) , 4,4*-methy- lenebis(2,6-di-tert-butylphenol) , and mixed sterically- hindered methylene bridged polyalkylphenols.

While the phenolic compounds used as component e) are known to possess antioxidant properties and thus are often used as antioxidants to protect fuels against premature oxi¬ dative degradation during storage, the available experimen¬ tal evidence tends to indicate that in the practice of this invention, this component contributes materially to the ef¬ fectiveness of the overall composition with respect to in- duction system deposit cleanliness.

Other components which preferably are used include the following:

Antioxidant. Suitable compounds which may be used to supplement the antioxidant effectiveness of component e) include amine antioxidants, sulfurized phenolic compounds, and organic phosphites, among others. For best results, the supplemental antioxidant should be composed predomi¬ nantly or entirely of an aromatic amine antioxidant such as the cycloalkyl-di-lower alkyl amines such as cyclohexyldi- methylamine, and the phenylenedia ines such as N,N'-di-sec- butyl-p-phenylenediamine.

Demulsifier. A wide variety of demulsifiers are avail¬ able for use in the practice of this invention, including, for example, polyoxyalkylene glycols, oxyalkylated phenolic resins, and like materials. Particularly preferred are mix¬ tures of polyoxyalkylene glycols and oxyalkylated alkylphe- nolic resins, such as are available commercially from Petrolite Corporation under the TOLAD trademark. One such proprietary product, identified as TOLAD 9310, is under- stood to be a mixture of these components dissolved in a solvent composed of heavy aromatic naphtha and isopropanol. This product has been found efficacious for use in the com¬ positions of this invention. However, other known demulsi- fiers can be used such as TOLAD 286K.

Corrosion Inhibitor. Here again, a variety of mater- ials are available for use as corrosion inhibitors in the practice of this invention. Thus, use can be made of dimer and tri er acids, such as are produced from tall oil fatty acids, oleic acid, linoleic acid, or the like. Products of this type are currently available from various commercial sources, such as, for example, the dimer and trimer acids sold under the HYSTRENE trademark by the Humko Chemical Division of Witco Chemical Corporation and under the EMPOL trademark by Emery Chemicals. Another useful type of cor¬ rosion inhibitor for use in the practice of this invention are the alkenyl succinic acid and alkenyl succinic anhy¬ dride corrosion inhibitors such as, for example, dodecenyl- succinic acid, dodecenylsuccinic anhydride, tetrapropenyl- succinic acid, tetrapropenylsuccinic anhydride, tetradecen- ylsuccinic acid, tetradecenylsuccinic anhydride, hexadecen- ylsuccinic acid, and hexadecenylsuccinic anhydride. Also useful are the half esters of alkenyl succinic acids having 8 to 24 carbon atoms in the alkenyl group with alcohols such as the polyglycols. Preferred materials are the suc¬ cinic acids or derivatives thereof represented by the for- mula:

R ⁵ 0

- « _c c o _R ⁴

R ³ C C 0 R ¹

R ²

wherein each of R², R³, R⁵ and R⁶ is, independently, a hydro¬ gen atom or a hydrocarbyl group containing 1 to 30 carbon atoms, and wherein each of R¹ and R⁴ is, independently, a hydrogen atom, a hydrocarbyl group containing 1 to 30 car- bon atoms, or an acyl group containing from 1 to 30 carbon atoms.

The groups R¹, R², R³, R*, R⁵, and R⁶ when in the form of hydrocarbyl groups, can be, for example, alkyl, cycloalkyl or aromatic containing groups. Preferably R¹, R², R³, R⁴ and R⁵ are hydrogen or the same or different straight-chain or branched-chain hydrocarbon radicals containing 1-20 carbon atoms. Most preferably, R¹, R², R³, R*, and R⁵ are hydrogen atoms. R⁶ when in the form of a hydrocarbyl group is pre¬ ferably a straight-chain or branched-chain saturated hydro- carbon radical.

Most preferred is a tetraalkenyl succinic acid of the above formula wherein R¹, R², R³, R* and R⁵ are hydrogen and R⁶ is a tetrapropenyl group.

Further embodiments of this invention involve the in- elusion in the additive concentrates and fuel compositions of a small quantity of a cyclopentadienyl manganese tricar- bonyl compound. Such compounds, when present in the fini¬ shed fuels, contribute materially to reduction of exhaust emissions, particularly emission of nitrogen oxides (NOx) . In addition, use of the cyclopentadienyl manganese tricar- bonyl compounds in the compositions of this invention re¬ sults in further improvements in induction system cleanli¬ ness, particularly cleanliness of inlet valves. Cyclopen¬ tadienyl manganese tricarbonyl compounds which can be used in the practice of this invention include cyclopentadienyl manganesetricarbonyl, methylcyclopentadienylmanganesetri¬ carbonyl, dimethylcyclopentadienyl manganese tricarbonyl, trimethylcyclopentadienyl manganese tricarbonyl, tetrameth- ylcyclopentadienyl manganese tricarbonyl, pentamethylcyclo- pentadienyl manganese tricarbonyl, ethylcyclopentadienyl manganese tricarbonyl, diethylcyclopentadienyl manganese tricarbonyl, propylcyclopentadienyl manganese tricarbonyl, isopropylcyclopentadienyl manganese tricarbonyl, tert-bu- tylcyclopentadienyl manganese tricarbonyl, octylcyclopen- tadienyl manganese tricarbonyl, dodecylcyclopentadienyl manganese tricarbonyl, ethylmethylcyclopentadienyl manga¬ nese tricarbonyl, indenyl manganese tricarbonyl, and the like, including mixtures of two or more such compounds. Preferred are the cyclopentadienyl manganese tricarbonyls which are liquid at room temperature such as ethylcyclo- pentadienyl manganese tricarbonyl, ethylcyclopentadienyl manganese tricarbonyl, liquid mixtures of cyclopentadienyl manganese tricarbonyl and methylcyclopentadienyl manganese tricarbonyl, mixtures of methylcyclopentadienyl manganese tricarbonyl and ethylcyclopentadienyl manganese tricarbo- nyl, etc. Preparation of such compounds is described in the literature, for example, U.S. 2,818,417. When used in the concentrates of this invention, the amount of the fuel-soluble cyclopentadienyl manganese tri¬ carbonyl compound is typically an amount such that the weight ratio of manganese to component (a) is in the range Of 0.0005:1 to 0.05:1.

The following examples in which all parts and percen¬ tages are by weight unless otherwise specified, illustrate the practice of this invention. These examples are not in¬ tended to limit, do not limit, and should not be construed as limiting the practice of this invention in its generic aspects.

Example 1 An additive concentrate of this invention is prepared by forming a blend of the following components: 204 parts of Mannich base detergent/dispersant;

400 parts of unhydrogenated 1-decene oligomer having a viscosity of 7.3 cSt at 100^βC; 245 parts of an aromatic solvent with a typical boil¬ ing range of 184-212"C and a viscosity of 1.36 cSt at 20*C;

50 parts of 2-ethyl-l-hexanol;

37.5 parts of a mixture of a tertiary butylated phenol antioxidant mixture containing a minimum of

75% 2,6-di-tert-butylphenol, 10-15% 2,4,6- tri-tert-butylphenol, and 15-10% of 2-tert- butylphenol; 61 parts of polypropene having a number average mole¬ cular weight of 810; and 2.5 parts of TOLAD 286K demulsifier. available from Petrolite Corporation.

- 11

SUBSTITUTE SHEET (RUL -26) The preferred Mannich base detergent/dispersant in this mix¬ ture is formed by reacting an alkylphenol having a number average molecular weight of approximately 905 with formal¬ dehyde and diethylene triamine.

Example 2

Three fuel compositions of this invention are formed by blending an additive concentrate formed as in Example 1 into three separate quantities of unleaded gasoline to re¬ spective concentrations of 750, 900 and 950 parts per mil- lion by weight.

Example 3 Example 1 is repeated substituting an equal amount of TOLAD 9310 demulsifying agent for the TOLAD 286K demulsify- ing agent.

Example 4

Example 1 is repeated except for the inclusion in the mixture of 5 parts of tetrapropenyl succinic acid and reduc¬ tion of the amount of 2-ethyl-l-hexanol to 45 parts.

Example 5 Example 1 is repeated with the exception that in one case the 2-ethyl-l-hexanol is replaced by an equal quantity of isooctanol and in a second case by an equal quantity of a mixture of primary amyl alcohols.

Example 6 In the standard Mercedes M102E Inlet Valve Cleanliness Test, a gasoline composition of this invention containing

- 12 -

SUBSTITUTE SHEET (RULE 2 750 ppm of a concentrate formed as in Example 1 (which gaso¬ line therefore contained 153 ppm of the Mannich base deter¬ gent/dispersant) gave an intake valve deposit reduction of 90.2% as compared to the additive-free base gasoline. In contrast, the same base gasoline containing 150 ppm of the same Mannich base detergent/dispersant as an additive mix¬ ture composed of 220 parts of the Mannich base, 450 parts of the same unhydrogenated 1-decene oligomer, 264 parts of the same aromatic solvent, and 66 parts of the same polypro- pene gave a reduction of only 78.8% when subjected to the same test procedure. This illustrates the advantages that arise by use of a combination of at least components a) through e) as required in the practice of this invention.

Example 7 A gasoline composition of this invention containing 925 ppm of a concentrate formed as in Example 3 gave a pas¬ sing result in a standard Renault F2N octane requirement test with the maximum change in knock limited spark advance of 8* at 3500 rpm full throttle.

Example 8

In a pair of duplicate tests, the performance of a fuel composition of this invention containing 750 ppm of an additive composition formed as in Example 3 gave intake valve deposit reductions of 77% and 73% as compared to the additive-free base fuel in the Opel Kadett Inlet Valve Test (CEC F-04-A-87) .

- 13 -

SUBSTITUTESHEET(RULE2$ Example 9 Performance of two fuels of this invention in the Volkswagen Wasserboxer Valve Stick No Harm Test was also examined. Passing performance indicated by no valve stick- ing was attained at 5°C by a gasoline containing 950 ppm of an additive composition formed as in Example 1. In another fuel of this invention, passing performance indicated by no valve sticking was attained at -20^βC by a gasoline contain¬ ing 1300 ppm of an additive composition formulated as in Example 3.

Example 10 In the Volkswagen Polo 1.05 liter Hz Engine High Speed Inlet Cleanliness Test, a gasoline composition of this in¬ vention containing 900 ppm of a concentrate formed as in Example 1 gave an inlet valve deposit reduction of 80.5% as compared to the additive-free base gasoline.

Example 11 An additive concentrate of this invention is prepared by forming a blend of the following components: 194.8 parts of Mannich base detergent/dispersant;

382 parts of unhydrogenated 1-decene oligomer having a viscosity of 7.3 cSt at 100*C; 233.8 parts of an aromatic solvent with a typical boil¬ ing range of 184-212"C and a viscosity of

47.8 parts of 2-ethyl-l-hexanol;

35.8 parts of a mixture of a tertiary butylated phenol antioxidant mixture containing a minimum of 75% 2,6-di-tert-butylphenol, 10-15 2,4,6- tri-tert-butylphenol, and 15-10% of 2-tert- butylphenol;

58.4 parts of polypropene having a number average mole¬ cular weight of 810; 2.4 parts of TOLAD 9310 demulsifier, available from

Petrolite Corporation; and

45 parts of a solution of 62% of methylcyclopentadi¬ enyl manganese tricarbonyl and 38% of a highly aromatic solvent, typically having a boiling range of 163-197"C, which solution has a manganese content in the range of 15.1 to 15.6%.

The preferred Mannich base detergent/dispersant for use in this mixture corresponds to that referred to in Example 1. The additive concentrate has a weight ratio of manganese to such Mannich base detergent/dispersant of approximately

0.036.

Example 12

Two additional gasoline composition of this invention were utilized in the standard Mercedes M102E Inlet Valve

Cleanliness Test. As compared to the additive-free base gasoline, the gasoline containing 900 ppm of an additive concentrate formed as in Example 1 gave a 96.3% reduction in intake valve deposits. On the same basis, the presence of 950 ppm of an additive concentrate formed as in Example

1 gave a reduction in intake valve deposits of 98.4%.

It will be appreciated that the compositions of this invention may be formed by blending together the components on an individual basis. Alternatively, two or more of the components may be formulated into the compositions of this invention in the form of a preformed mixture. For example, the Mannich base detergent/dispersant used as component a) may be produced in an aromatic hydrocarbon to be utilized as component c) . Moreover, by suitably adjusting the pro¬ portions of the reactants, the finished product may also contain branched chain alkene hydrocarbon such as unreacted polypropene.

The additive concentrates are normally employed in amounts providing from 20 to 700, and preferably from 60 to 400 parts by weight of the Mannich base detergent/disper¬ sant per million parts by weight of the base fuel. Gener¬ ally, the additive concentrates of this invention contain from 10 to 40, and preferably from 20 to 30 weight percent of the Mannich base detergent/dispersant based on the total weight of the concentrate.

The fuels of this invention may typically contain from 5 to 80 and preferably from 15 to 40 ppm by weight of sup¬ plemental antioxidant [i.e. , antioxidant in addition to com- ponent (e) ] , from 0.5 to 30 and preferably from 1 to 10 ppm by weight of demulsifier, and, if used, from 1 to 25 and preferably from 1 to 10 ppm by weight of corrosion inhibi¬ tor. In the additive concentrates of this invention, the amounts of these various components will be proportioned such that at the recommended dosage level of the concen¬ trate, the fuel will contain the desired amount of each such component within the foregoing ranges specified in this paragraph.

All proportions given throughout this document are in terms of active content of the component. Thus if the de¬ tergent/dispersant or any other component as supplied is diluted with a solvent, the amount of the solvent should be excluded from consideration in calculating proportions for use. Care should be exercised in selecting components sup¬ plied in liquid diluents or carriers to be sure that such diluents or carriers do not materially detract from or otherwise materially interfere with the performance of the composition.

Numerical ranges of concentrations and proportions given herein are susceptible to minor variations which do not materially alter the performance of the particular com¬ position under consideration.

As used herein, the term "fuel-soluble" means that the material under discussion can be dissolved in the particu¬ lar fuel under consideration to a concentration at least sufficient to achieve the minimum concentration level spe¬ cified herein. Preferably the component has a significant¬ ly higher solubility in the fuel than such minimum concen¬ tration level. However, the term does not mean that the component must be soluble in all proportions in the fuel.

Claims

Claims:

1. A fuel additive concentrate for minimizing induc- tion system deposits in an internal combustion engine, which concentrate comprises at least the following compo- nents: (a) at least one fuel-soluble Mannich base detergent/dis- persant; (b) unhydrogenated poly-α-olefin oligomer having a visco- sity in the range of 5 to 10 cSt at 100°C formed by oligomerization of C₈ to C₁₂ α-olefin; (c) aromatic hydrocarbon boiling in the range of 160 to 300"C and having a viscosity in the range of 1.2 to 2.0 cSt at 25^*C; (d) at least one fuel-soluble alkanol having in the range of 5 to 13 carbon atoms per molecule; and (e) at least one fuel-soluble sterically hindered alkyl- substituted mononuclear or non-fused ring polynuclear phenolic compound in which there are in the range of 10 to 20 carbon atoms per hydroxyl group and in which there is one and only one hydroxyl group attached to each aromatic nucleus; wherein the weight ratio of (e) : (a) is in the range of 0.05:1 to 0.5:1, the weight ratio of (d) : (a) is in the range of 0.1:1 to 2:1, the weight ratio of (c) : (a) is in the range of 0.1:1 to 3:1, and the weight ratio of (b) : (a) is in the range of 0.2:1 to 8:1.

2. A concentrate according to Claim 1 wherein the weight ratio of (e) : (a) is in the range of 0.05:1 to 0.25:1, the weight ratio of (d) : (a) is in the range of 0.1:1 to 1:1, the weight ratio of (c) : (a) is in the range of 1:1 to 2:1, and the weight ratio of (b) : (a) is in the range of 1:1 to 4:1.

3. A concentrate according to Claim 1 wherein the weight ratio of (e) : (a) is in the range of 0.08:1 to 0.12:1, the weight ratio of (d) : (a) is in the range of 0.1:1 to 0.5:1, the weight ratio of (c) : (a) is in the range of 1:1 to 2:1, and the weight ratio of (b) : (a) is in the range of 1.5:1 to 3:1.

4. A concentrate according to any of the preceding claims wherein the unhydrogenated poly-α-olefin oligomer is an oligomer of 1-decene having a viscosity in the range of 5.5 to 7.5 CSt at lOO'C.

5. A concentrate according to any of the preceding claims further comprising at least one fuel-soluble pheny- lene diamine antioxidant, or at least one fuel-soluble de- mulsifying agent, or at least one fuel-soluble corrosion inhibitor, or a combination of any two or all three of these additional components.

6. A concentrate according to any of the preceding claims wherein the detergent/dispersant is a Mannich base formed by reaction of an alkylphenol in which the alkyl group has a number average molecular weight in the range of 750 to 1200, polyalkylene polyamine and formaldehyde or a formaldehyde precursor.

7. A concentrate according to Claim 6 wherein the alkyl group of the alkylphenol is derived from polypropene having a number average molecular weight in the range of 800 to 950 and wherein the polyalkylene polyamine is di- ethylene triamine.

8. A concentrate according to any of the preceding claims wherein the concentrate further comprises branched chain alkane or alkene hydrocarbon having a number average molecular weight in the range of 750 to 1200 in an amount such that the weight ratio of said hydrocarbon to component (a) is in the range of 0.1:1 to 1:1.

9. A concentrate according to Claim 8 wherein said hydrocarbon is polypropene or hydrogenated polypropene and wherein said weight ratio is in the range of 0.1:1 to 0.5:1.

10. A concentrate according to any of the preceding claims wherein component (c) is aromatic hydrocarbon boil- ing in the range of 175 to 220*C and having a 50% boiling temperature in the range of 185 to 195"C, said aromatic hy- drocarbon containing from 75 to 80 volume percent of C₉ to C₁₂ alkylbenzenes, from 12 to 18 volume percent indans and tetrahydronaphthalenes, 6 to 9 volume percent naphthalenes and less than 1 volume percent of benzene as determined by gas chromatography.

11. A concentrate according to any of the preceding claims wherein component (d) is a branched chain alkanol having 7 to 10 carbon atoms in the molecule.

12. A concentrate according to Claim 11 wherein the branched chain alkanol is 2-ethyl-l-hexanol.

13. A concentrate according to any of the preceding claims wherein the phenolic compound is a mononuclear mono- hydric alkyl phenol having in the range of 10 to 18 carbon atoms per molecule.

14. A concentrate according to Claim 13 wherein the alkyl phenol is a mixture of tertiary butylated phenols comprising at least 75 weight percent of 2,6-di-tert-butyl- phenol.

15. A concentrate according to any of the preceding claims further comprising at least one fuel-soluble cyclo- pentadienyl manganese tricarbonyl compound in an amount such that the weight ratio of manganese to component (a) is in the range of 0.001:1 to 0.05:1.

16. A liquid fuel composition which comprises a hydro- carbonaceous fuel containing the components in accordance with any of Claims 1-15 in an amount at least sufficient to minimize induction system deposits from an internal combus- tion engine.

17. A fuel composition in accordance with Claim 16 wherein the hydrocarbonaceous fuel is gasoline.

18. The use of a fuel additive concentrate in accor- dance with any of Claims 1-15 in a hydrocarbonaceous fuel to minimize induction system deposits in an internal combustion engine.