DE69202642T2 - Compositions for octane demand increase control. - Google Patents

Description

The present invention relates to the control of the increase in the requirement with regard to the octane number in internal combustion engines (gasoline engines). In particular, the present invention relates to fuel compositions as well as fuels made from gasoline and fuel mixtures for internal combustion engines (gasoline engines) which can bring about a reduction and at least a minimization of the increase in the requirement with regard to the octane number during engine operation.

As is well known, fuels for internal combustion engines (gasoline engines) contain several additives to improve engine performance. However, these additives often cause undesirable deposits, which over time make a higher octane rating necessary for internal combustion engines. These deposits also generally form in the combustion chamber, on the intake valves and on the injectors during engine operation. It is an object of this invention to provide compositions that can reduce the problem of an increase in octane rating requirements. A further object of the invention is to provide compositions that can reduce deposits that are already present due to previous operation with fuels that cause such deposits. Furthermore, it is an object of the invention to provide compositions which can reduce the clogging of injection nozzles and which do not contribute significantly to the formation of deposits on intake valves.

The demand for environmentally friendly fuels and fuel mixtures and the fitting of more and more vehicles with fuel injectors to achieve higher efficiency and a reduction in emissions from petrol engines has led to a need for fuels and fuel mixtures that reduce or eliminate deposits on fuel injectors, intake valves and the surfaces of combustion chambers. These deposits not only require fuels with a higher octane rating, but also generally impede the supply of fuel to the engine and cause the valves to stick. To reduce the amount of deposits on the valves of the fuel injectors, detergent additives specially developed for this purpose have been added to petrol. Although these detergent additives have made it possible to achieve a considerable reduction in the deposits that previously hindered the operation of petrol injection engines, this highly desirable cleaning effect does not necessarily apply to preventing deposits on other internal engine components, such as intake valves, or to cleaning these other parts of such deposits. These substances can actually lead to a higher octane rating being required for the engine. Therefore, detergent additives are required that do not cause contamination of the injection nozzles, as well as allowing effective control of deposits on other parts of internal combustion engines (gasoline engines).

Figure 1 shows the change in octane requirement depending on the addition of additives in pounds/1000 feet (kg/m³).

The present invention relates to a fuel additive concentrate for controlling octane demand in internal combustion engines (gasoline engines) which comprises the reaction product of (i) polyamine and (ii) at least one acyclic hydrocarbyl substituted succinic acid as an acylating agent, a non-hydrotreated poly-α-olefin and optionally a mineral oil having a viscosity index of less than about 90 and a volatility of about 50% or less according to the test procedure described below.

In one embodiment of this invention, the substance contains a major amount of hydrocarbons in the boiling range of gasoline or mixtures of hydrocarbons and oxygenated substances or oxygenated substances consisting of the following components: (a) a minor but effective amount of a fuel additive consisting of the reaction product of (i) polyamine and (ii) at least one acyclic hydrocarbyl substituted succinic acid as an acylating agent, (b) a non-hydrotreated liquid poly-α-olefin having a volatility of about 50% or less, according to the method described below Test Procedure, and (c) optionally, a mineral oil (A) having a viscosity index of less than about 90 and a volatility of 50% or less according to the Test Procedure described below, an antioxidant (B), a demulsifier (C) or an aromatic hydrocarbon solvent (D), a corrosion inhibitor (E), or any combination of two, three, four, or all five of components (A), (B), (C), (D), and (E). Other performance enhancing additives, such as combustion enhancers or octane requirement enhancers, may also be blended.

A further embodiment of the present invention is a method for controlling octane demand escalation in internal combustion engines (spark ignition engines) in which a fuel composition is prepared comprising (a) a major amount of an unleaded gasoline and (b) a minor but effective amount of an octane demand escalation control mixture, the mixture comprising (i) the reaction product of polyamine and at least one acyclic hydrocarbyl substituted succinic acid as an acylating agent, (ii) a non-hydrotreated liquid poly-α-olefin having a volatility of 50% or less according to a test method described below, and (iii) optionally a mineral oil having a viscosity index of less than about 90 and a volatility of 50% or less according to a test method described below, whereby the octane demand escalation of a combustion engine is effectively controlled.

These and other embodiments of the present invention can be found in the following description and the appended claims.

Detergents/Dispersants. As previously mentioned, the fuel additive concentrate of the present invention contains (a) as a detergent or dispersant (i) the reaction product of polyamine and (ii) at least one acyclic hydrocarbyl substituted succinic acid acylating agent, (b) a non-hydrotreated liquid poly-α-olefin having a volatility of 50% or less, and (c) optionally a mineral oil having a viscosity index of less than about 90 and a volatility of 50% or less. The polyamine reactant can be either one or more straight, branched or cyclic chain alkylene polyamines or a mixture of straight, branched and/or cyclic polyamines, each alkylene group having between 1 and 10 carbon atoms. Preferably, a polyamine is used which has between 2 and 10 nitrogen atoms per molecule, or a mixture of polyamines which have on average between 2 and 10 nitrogen atoms per molecule. A polyamine or a mixture of polyamines with 3 to 7 nitrogen atoms is particularly preferred, with triethylenetetramine or a combination of ethylenepolyamines close to triethylenetetramine being most preferred. When selecting a suitable polyamine, the compatibility of the resulting detergent or dispersant with the gasoline fuel mixture with which it is mixed.

The most preferred polyamine, triethylenetetramine, normally contains a commercial blend which has a general overall composition close to that of triethylenetetramine, but which may also contain minor amounts of branched and cyclic polyamines as well as straight chain polyethylenepolyamines such as diethylenetriamine and tetraethylenepentamines. Best results are obtained when the proportion of triethylenetetramine-enriched straight chain polyethylenepolyamine in these blends is at least 50 and preferably at least 70% by weight.

The acylating agent which is reacted with the polyamine is an acyclic hydrocarbyl substituted succinic acid, the substituent containing on average between 50 and 100 (preferably 64 to 80) carbon atoms. In order to achieve the object of the invention, it is important that the acyclic hydrocarbyl substituted succinic acid which serves as the acylating agent has an acid number between 0.7 and 1.1 (preferably between 0.8 and 1.0, or most preferably an acid number of 0.9).

In order to achieve the objectives of the invention, the molar ratio between the acylating agent and the polyamine in the reaction product of (i) and (ii) must preferably be greater than 1:1. The preferred molar ratio between Acylating agent and polyamine in the reaction product should be between 1.5:1 and 2.2:1, more preferably between 1.7:1 and 1.9:1, with the best ratio being 1.8:1.

The acid number of the acylating agent consisting of an acyclic hydrocarbyl substituted succinic acid is determined in a conventional manner, i.e. by titration, and is expressed as mg KOH/g of product. It should be noted that for this determination the total acylating agent is used in the presence of any unreacted olefin polymer (e.g. polyisobutene).

The acyclic hydrocarbyl substituent of the acylating agent should preferably be an alkyl or an alkenyl group with the required number of carbon atoms specified above. Alkenyl substituents derived from poly-α-olefin homopolymers or copolymers with the corresponding molecular weight (e.g. propene homopolymers, butene homopolymers, C3 and C4 α-olefin copolymers) are suitable for this purpose. However, the most suitable substituent is a polyisobutenyl group from polyisobutene with a number average molecular weight of 700 to 1200, preferably 900 to 1100, most preferably 940 to 1000 (the molecular weight being determined by gel chromatography).

Acylating agents consisting of a succinic acid substituted with acyclic hydrocarbyl, and methods for preparing these acylating agents and their use for Preparation of succinimide are well known to the person skilled in the art and are described in detail in the relevant patent literature, such as in the following US patents:

3,018,247 3,231,587 3,399,141 3,018,250 3,272,746 3,401,118 3,018,291 3,287,271 3,513,093 3,172,892 3,311,558 3,576,743 3,184,474 3,331,776 3,578,422 3,185,704 3,341,542 3,658,494 3,194,812 3,346,354 3,658,495 3,194,814 3,347,645 3,912,764 3,202,678 3,361,673 4,110,349 3,215,707 3,373,111 4,234,435 3,219,666 3,381,022

When using the well-known processes described in these patents, care must be taken with regard to the present invention that, in accordance with the values given here, the hydrocarbyl substituent of the acylating agent has the required number of carbon atoms, that the acylating agent has the required acid number, that the acylating agent is reacted with the required polyethylene polyamine and that the reactants are used in such a ratio that the resulting succinimide contains the chemically bonded reactants in the required proportions. By combining the features given above, preparations can be obtained which contain detergents or dispersants which are exceptionally effective in controlling or reducing deposits on induction systems that form during engine operation and enable correspondingly good demulsification.

As mentioned in the above-identified patents, the acylating agents consisting of acyclic hydrocarbyl-substituted succinic acid include the following components: the hydrocarbyl-substituted succinic acids, the hydrocarbyl-substituted succinic anhydrides, the hydrocarbyl-substituted succinic halides (particularly the acid fluorides and chlorides), as well as the esters of succinic acids substituted with hydrocarbyl and low molecular weight alcohols (e.g. alcohols with up to 7 carbon atoms), i.e. hydrocarbyl-substituted compounds that can be used as carboxyl acylating agents. Of these compounds, hydrocarbyl-substituted succinic acids and hydrocarbyl-substituted succinic anhydrides, as well as mixtures of these acids and anhydrides, are generally preferred, with hydrocarbyl-substituted succinic anhydrides being particularly preferred.

The acylating agent used to prepare the detergents or dispersants of the present invention is preferably prepared by reacting a poly-α-olefin of appropriate molecular weight (with or without chlorine) with maleic anhydride. However, similar carboxylic reactants may also be used, such as maleic acid, fumaric acid, Malic acid, tartaric acid, itaconic acid, itaconic anhydride, citraconic acid, citraconic anhydride, mesaconic acid, ethylmaleic anhydride, dimethylmaleic anhydride, ethylmaleic acid, dimethylmaleic acid and hexylmaleic acid, including the corresponding acid halides and the low molecular weight aliphatic esters.

The reaction between components (i) and (ii) is generally carried out at temperatures between 80°C and 200°C, preferably between 140°C and 180°C, to form a succinimide. This reaction may optionally be carried out in the presence of an additional diluent or a liquid reactant such as a mineral lubricating oil solvent. Suitable solvent oils are natural and synthetic unmixed base lubricants having a volatility of 50% or less according to the test procedure described below. Suitable synthetic diluents include polyesters, hydrogenated or unhydrogenated poly-α-olefins (PAO), such as a hydrogenated or unhydrogenated dec-1-ene oligomer. Blends of mineral and synthetic oils are also suitable for this purpose. In a particularly preferred embodiment, the reactions are carried out essentially without an additional diluent oil, so that the reaction product contains essentially no paraffinic mineral oils, i.e. the reaction product contains less than 1% by weight of paraffinic mineral oil.

The term succinimide refers here to the complete reaction product of components (i) and (ii) and compounds in which the product may contain amide, amidine and/or salt linkages in addition to those imide linkages resulting from the reaction of a primary amino group with an anhydride moiety.

Diluent oil. One of the main features of the present invention is the use of a non-hydrotreated poly-α-olefin having a volatility of 50% or less and optionally a mineral oil having a viscosity index of less than 90 and a volatility of 50% or less as a diluent for the preparation of a fuel additive concentrate or as a major component in blends of gasoline and succinimide reaction product. Surprisingly and quite unexpectedly, it has been discovered that by blending a certain succinimide and a certain poly-α-olefin with gasoline in certain proportions - which may or may not contain certain mineral oils - the increase in octane requirements of internal combustion engines can be effectively controlled. "Effectively controlled" means that the formation of deposits that lead to increased octane requirements is significantly reduced and/or that in engines that already have heavy deposits to begin with, the deposits are significantly reduced when the process described here is used.

For the compositions and methods of the present invention, the poly-α-olefins (PAO) should preferably be non-hydrotreated poly-α-olefins. In the Poly-α-olefins are non-hydrogenated or non-hydrotreated oligomers, preferably trimers, tetramers and pentamers of α-olefin monomers having from 6 to 12, generally 8 to 12, and preferably 10 carbon atoms. The synthesis of these oligomers is described in Hydrocarbon Processing, February 1982 issue, pages 75 ff., and consists essentially of the catalytic oligomerization of straight, short chain alpha-olefins (suitably prepared by catalytic treatment of ethylene). The type of particular PAO depends in part on the carbon chain length of the starting alpha-olefin and on the oligomer structure. The exact molecular structure may vary somewhat depending on the exact conditions of oligomerization, causing the resulting PAOs to have different physical properties. However, since physical properties, particularly viscosity, are the main criterion for determining whether a particular PAO is suitable as a starting lubricating oil, a distinction is generally made between the various products and a classification is made according to viscosity. According to the present invention, poly-α-olefins having a viscosity between 2 and 20 cSt (measured at 100°C) are particularly suitable for the preparation of fuel additive compositions according to the present invention. The poly-α-olefin preferably has a viscosity of at least 8 cSt, most preferably about 10 cSt, at 100°C. Another main feature of this invention is the volatility of the poly-α-olefin, which can be determined by the method described below.

The volatility of mineral oils and poly-α-olefins useful in the present invention is determined by the following procedure: Mineral oil or poly-α-olefin (110-135 grams) is charged to a 250 mL, three-neck, round-bottom flask having a threaded opening for the insertion of a thermometer. Flasks of this type can be obtained from Ace Glass (catalog no. 6954-72 with 20/40 mounts). A stir bar with a 19 mm wide by 60 mm long Teflon sheet (Ace Glass catalog no. 8085-07) is inserted through the opening in the center of the flask. The mineral oil or poly-α-olefin in the flask is heated to 300°C with stirring at 150 rpm in an oil bath for 1 hour. Meanwhile, the free space above the oil in the flask is flushed with 7.5 l of air/h. The volatility of the oil determined in this way is expressed as a weight percent of the substance lost, based on the total initial weight of the material being examined.

Mineral oils with suitable volatility are naphthenic and asphaltic oils of the type commonly found along the Gulf Coast, such as Coastal Pale type oils. A typical Coastal Pale may contain between 3 and 5 wt.% polar material, between 20 and 35 wt.% aromatic hydrocarbons, and between 50 and 75 wt.% saturated hydrocarbons, and have a molecular weight between 300 and 600. Asphaltic oils are oils that contain high molecular weight (approximately > 800) and high polarity components and little or no pure hydrocarbon components. The most common polar components generally found in such asphaltic oils include carboxylic acids, phenols, amides, carbazoles, and pyridine benzenesulfonates. Asphaltenes typically contain 40-50 weight percent aromatic carbon and have a molecular weight of several thousand. Deposits of asphaltic oils are generally found along the west coast. At a temperature of 38ºC (100ºF), the mineral oil should preferably have a viscosity of less than about 346 cSt (1600 SUS), more preferably less than 325 cSt (1500 SUS), and most preferably between 173 and 315 cSt (between 800 and 1500 SUS). The viscosity index of the mineral oil should ideally be less than 90, more preferably less than 70, and most preferably between 30 and 60.

A particularly important feature of the present invention is the weight ratio between succinimide and diluent oil in the mixtures described. It has been found that a weight ratio of less than 1 part succinimide to 3 parts diluent oil meets the purpose of the present invention. The weight ratio between succinimide and diluent oil is preferably between 1:1.5 and 1:3.0, with the best weight ratio being between 1:1.2 and 1:2.5.

The diluent oil preferably contains between 30 and 80% by weight mineral oil and between 70 and 20% by weight non-hydrotreated poly-α-olefin. A diluent oil containing 50 to 65% by weight mineral oil and 35 to 50% by weight non-hydrotreated poly-α-olefin is preferred. However, a Diluent oil containing 55 to 60 percent naphthenic mineral oil and 40 to 45 percent non-hydrotreated poly-α-olefin.

Antioxidant. In practice, various compounds can be used as antioxidants for the present invention. These include phenol-containing antioxidants, amine-containing antioxidants, sulfurized phenol compounds and organic phosphites, etc. The best results are obtained when the antioxidant consists mainly or entirely of either (1) a hindered phenol antioxidant such as 2-tert-butylphenol, 2,6-di-tert-butylphenol, 2,4,6-tri-tert-butylphenol, 4-methyl-2,6-di-tert-butylphenol, 4,4'-methylene-bis-(2,6-di-tert-butylphenol) and mixed methylene-bridged polyalkylphenols, or (2) an aromatic amine antioxidant such as low molecular weight cycloalkyl-di-alkylamines and phenylenediamines, or a combination of one or more of these phenol antioxidants and one or more of these amine antioxidants. Particularly preferred for the practice of the present invention are tertiary butylated phenols such as 2,6-di-tert-butylphenol, 2,4,6-tri-tert-butylphenol and 0-tert-butylphenol.

Demulsifier. In practice, a wide range of different demulsifiers can be used for the present invention, such as polyoxyalkylene glycols, oxyalkylated phenolic resins and similar substances. Particularly preferred are mixtures of polyoxyalkylene glycols and oxyalkylated alkylphenol resins, available, for example, from Petrolite Corporation under the trademark TOLAD. One such product, called TOLAD 9308, consists of a mixture of these components dissolved in a solvent of heavy aromatic naphtha and isopropanol. This product has been found to be effective in the compositions of the present invention. However, other demulsifiers, such as TOLAD 286, may also be used.

Corrosion inhibitors. Again, there is a wide range of different substances that can be used in practice as corrosion inhibitors for the present invention. For example, dimer and trimer acids can be used, which are obtained, for example, from tall oil fatty acids, oleic acid, linoleic acid and the like. Products of this type are currently available from several suppliers. Dimer and trimer acids are sold, for example, under the trademark HYSTERENE by the Humko Chemical Division of Witco Chemical Corporation and under the trademark EMPOL by Henkel Chemicals. Other useful corrosion inhibitors that can be used in practice for the invention are corrosion inhibitors made from alkenylsuccinic acid and alkenylsuccinic anhydrides, such as tetrapropenylsuccinic acid, tetrapropenylsuccinic anhydride, tetradecenylsuccinic acid, tetradecenylsuccinic anhydride, hexadecenylsuccinic acid and hexadecenylsuccinic anhydride. Also useful are half esters of alkenylsuccinic acids with 8 to 24 carbon atoms in the alkenyl group and alcohols, such as polyglycols. Preferred substances are succinic acids or derivatives thereof that correspond to the following formula:

wherein R², R³, R⁵ and R⁶, each independently of one another, represent a hydrogen atom or a hydrocarbon group having 1 to 30 carbon atoms, and wherein R¹ and R⁴, each independently of one another, represent a hydrogen atom, a hydrocarbon group having 1 to 30 carbon atoms or an acyl group having 1 to 30 carbon atoms.

When present as a hydrocarbyl group, the groups R¹, R², R³, R⁴, R⁵ and R⁶ can be, for example, alkyl, cycloalkyl, or aromatic-containing groups. R¹, R², R³, R⁴, and R⁵ are preferably hydrogen or either the same or different straight-chain or branched-chain hydrocarbon radicals containing from 1 to 20 carbon atoms. Ideally, R¹, R², R³, R⁵, and R⁵ are hydrogen atoms. When R⁴ is present as a hydrocarbyl group, the group is preferably a straight-chain or branched-chain saturated hydrocarbon radical.

Ideally, a tetraalkenylsuccinic acid having the formula given above is used, where R¹, R², R³, R⁴ and R⁵ are hydrogen and R⁶ is a tetrapropenyl group.

Aromatic hydrocarbon solvent.

A wide range of aromatic hydrocarbon solvents can be used for the present invention, such as benzene, alkyl-substituted benzene or mixtures thereof. Mixtures of o-, p- and m-xylenes and mesitylene as well as aromatics with a higher boiling point, such as Aromatic 150 from Chemtec, are particularly advantageous. However, other mixtures of aromatic hydrocarbon solvents can also be used.

The proportions of the various substances for the additive concentrate and the distillate fuels can be varied within certain limits. However, the best results are obtained when these compositions contain between 10 and 50 parts by weight (preferably between 20 and 35 parts by weight) of succinimide, up to 75 parts by weight (preferably between 50 and 65 parts by weight) of diluent oil, 0 to 5 parts by weight (preferably between 1 and 3 parts by weight) of antioxidant, 0 to 10 parts by weight (preferably between 0.3 and 3 parts by weight) of demulsifier, between 0 and 75 parts by weight (preferably between 5 and 25 parts by weight) of aromatic hydrocarbon solvent and between 0 and 5 parts by weight (preferably between 0.025 and 1.0 parts by weight) of corrosion inhibitor per hundred parts by weight of the fuel additive composition.

The above-mentioned mixtures of the present invention are preferably used for hydrocarbon mixtures in the boiling range of gasoline, or for mixtures of hydrocarbon and oxygenated substances or for oxygenated substances, but are also suitable for use with medium distillate fuels, in particular diesel fuels and fuels for gas turbine engines. The composition of these fuels is well known to the person skilled in the art, so that no further comments are required. Oxygenated substances are understood here to mean alkanols and ethers, such as methanol, ethanol, propanol, methyl tert-butyl ether, ethyl tert-butyl ether, tert-amyl methyl ether or combinations thereof. Of course, the source fuels can also contain other, frequently used ingredients, such as cold start aids, dyes, metal deactivators, substances to improve the octane number and to improve the cetane number, additives for emission control and antioxidants.

In determining the fuel compositions of the present invention, the additive amounts must be determined so as to reduce or prevent an increase in the octane requirement of internal combustion engines. Generally, the fuel additive is selected from a succinimide, a non-hydrotreated poly-α-olefin having a Volatility of 50% or less and a mineral oil with a viscosity index of less than 90 and a volatility of 50% or less for unleaded gasoline are used in smaller quantities so that the gasoline forms the main component of the fuel. A smaller quantity here means less than 3000 parts per million gasoline parts, preferably less than 1500 parts per million gasoline parts. Ideally, the additive is present in a ratio of 600 to 1200 parts per million gasoline parts. The other components, which are preferably used together with the detergent or dispersant and the diluent oil, are mixed into the fuel either individually or as various combinations thereof. In any case, however, it is preferable to mix all the components together in an additive concentrate according to the invention since in this case the compatibility of the substance combinations with one another can be utilized.

The following examples, in which all information refers to parts by weight, illustrate the present invention but are not intended to limit it.

example 1

A fuel additive concentrate is made from the following substances:

(a) 50 parts by weight of a detergent/dispersant prepared by reacting polyisobutenyl succinic anhydride having an acid number of 1.1 (prepared by reacting maleic anhydride with polyisobutene having a number average molecular weight of 950) with a commercially available mixture that is close to triethylenetetramine, with a molar ratio of 2:1 in each case.

(b) 75 parts of a naphthenic mineral oil, designation H-4053, available from Witco Corporation,

(c) 25 parts of a non-hydrotreated PAO with a viscosity of 10 cSt,

(d) 3.5 parts of a demulsifier mixture consisting of alkylarylsulfonates, polyoxyalkylene glycols and oxyalkylated alkylphenol resins in alkylbenzenes (TOLAD 9308),

(e) 2 parts of tetrapropenylsuccinic acid, prepared as a 50% solution in light mineral oil.

This concentrate is mixed with gasoline and diesel fuels in concentrations of 0.44 kg/m³ (155.5 PTB).

Example 2

Example 1 is repeated with the components used therein, but with 60 parts by weight of (a), 60-80 parts by weight of (b) and 40-60 parts by weight of (c) and additionally 4 parts of an antioxidant mixture of tertiary butylated phenol containing at least 75% 2,6-di-tert-butylphenol, 10-15% 2,4,6-tri-tert-butylphenol and 15-10% 2-tert-butylphenol, 3 parts of Tolad 286 and 2 parts of tetrapropenylsuccinic acid, which is in the form of a 50% solution in light mineral oil. This mixture is then mixed with gasoline in a ratio of 0.51 kg/m³ (180 PTB).

Example 3

Example 1 is repeated with the components used therein, but using 75 parts (a), 75-100 parts (b) and 75 parts (c) and additionally 5 parts of an antioxidant mixture of tertiary butylated phenol containing at least 75% 2,6-di-tert-butylphenol, 10-15% 2,4,6-tri-tert-butylphenol and 15-10% 2-tert-butylphenol, 3.5 parts Tolad 9308 and 2 parts tetrapropenyl succinic acid, which is in the form of a 50% solution in light mineral oil. This mixture is then mixed with gasoline at a ratio of 0.64 to 0.71 kg/m³ (225-250 PTB).

Example 4

The effectiveness of the compositions of the present invention in reducing or preventing an increase in octane requirement in an internal combustion engine is demonstrated by a series of tests conducted on a 2.3 liter Ford engine. The engine was operated for 112 hours with the specified fuel additive using conventional methods for determining octane requirement increase. Figure 1 shows the effects of various additive concentrates on the octane requirement of the 2.3 liter Ford engine.

The effectiveness of the compositions of the present invention in reducing deposits on induction systems was demonstrated in a series of standard engine tests carried out on the white spirits having the formulations given in Examples 1, 2 and 3.

Example 5

In a series of tests, the Briggs and Stratton Engine Test, the compositions given in Example 1 were compared with an untreated gasoline. The tests used a 3 hp Briggs & Stratton engine and SAE 10W-40 oil. The test duration was 150 hours. After breaking in the engine at various speeds and loads, the engine was operated with a load of 500 W (0.67 hp) at 3000 rpm. The spark plug temperature was controlled to about 204ºC (400ºF). The oil level was checked frequently and an oil change was made after 80 hours. Before and after each test, the valves were weighed to determine the amount of deposits. Phillips J brand unleaded, untreated gasoline was used for the test and the amount of deposits on the intake valves was measured. The results of the tests conducted under the same test conditions are shown in Table 1. Table 1 Component kg/m3 (PTB) Valve deposits (mg)

Example 6

In a further series of tests on a 2.3 litre 4 cylinder Ford engine using Union Oil Clear unblended fuel, test fuels having the compositions given in Example 2 were compared with an untreated fuel. The test duration was 112 hours. In preparation, the engine was run for 1 minute at 2000 rpm with a load of 0-3 kW (0-4 BHP) and then for 3 minutes at 2800 rpm and 28 kW (37 BHP). The oil was checked every 8 hours and changed after 56 hours. At the end of the tests, the inlet valves and ports were removed and weighed. Table 2 shows the results of the tests on treated and untreated fuels carried out under the same test conditions. Table 2 Component kg/m3 (PTB) Average deposits (mg)

Example 7

In another series of tests, a BMW 318 with automatic transmission and a 1.8 l PFI engine was driven on untreated and treated Mobil regular unleaded petrol over a distance of 16000 km (10000 miles). During the test, the BMW was driven 10% at city speeds in stop-and-go traffic, 20% at moderate speeds with few stops and 70% of the time driven at highway speeds of 105 km/h (65 MPH). To achieve the required mileage, the BMW was driven 20 hours per day or 1300 km (800 miles) per day. The oil change was carried out according to the BMW service intervals. After 8000 and 16000 km (5000 and 10000 miles respectively) the intake valves were removed and weighed. Table 3 shows the results of the tests with various additive concentrates. Table 3 Component kg/m3 (PTB) Average deposits (mg)

Example 8

In order to determine the extent to which the compositions of the present invention can prevent or at least help to control valve sticking, a series of tests were carried out with the compositions given in Example 3. The standard valve sticking test was used for this with a water-cooled VW boxer engine. The VW boxer test consists of 3 consecutive test runs with 13 test cycles, each test run being carried out for 21 minutes with load and speed changes and stops. Before the test runs, the engine was prepared accordingly using the standard procedures. After each During the test run, the engine was stopped and the temperature in the test cells was maintained at 5ºC for at least 16 hours. Any loss of compression was considered a failure. The compression of each cylinder was then measured at 5ºC. Table 4 shows the results of the test for valve sticking when an engine was operated with fuel containing the detergents or additives of the present invention. Table 4 Compression (in bar) Cylinder test run

Claims (14)

1. Fuel additive concentrate for controlling the increase in requirements regarding the octane number in internal combustion engines (gasoline engines), which contains the following components: (a) the reaction product of (i) polyamine and (ii) at least one acyclic hydrocarbyl-substituted succinic acid as acylating agent; (b) a non-hydrotreated liquid poly-α-olefin oligomer having a volatility of 50% or less and (c) optionally (A) a mineral oil having a viscosity index of less than about 90 and a volatility of 50% or less, such volatility being expressed as a weight percent of the substance lost based on the total initial weight of the material being tested, when such material is heated in a 250 ml round bottom flask to 300ºC for one hour with stirring at 150 rpm while purging the free space above the material in the flask with 7.5 l of air/h. 2. Concentrate according to claim 1, which further comprises a smaller but effective amount (B) an antioxidant; (C) a demulsifier; (D) an aromatic hydrocarbon solvent; (E) a corrosion inhibitor or contains any combination of components (A), (B), (C), (D) and (E). 3. Concentrate according to claim 2, wherein the antioxidant consists of a hindered (sterically hindered) phenol. 4. Concentrate according to claim 3, wherein the antioxidant consists of a tertiary butylated phenol containing at least 75% 2,6-di-tert-butylphenol, 10-15% 2,4,6-tri-tert-butylphenol and 15-10% 2-tert-butylphenol. 5. Concentrate according to claim 2, which contains the mineral oil (A), the demulsifier (C) and the corrosion inhibitor (E). 6. Concentrate according to claim 2, 3 or 4, which contains the mineral oil (A), the antioxidant (B), the demulsifier (C) and the corrosion inhibitor (E). 7. A concentrate according to any one of claims 1 to 6, in which the weight ratio of (a) to (b) plus (c) is less than 1:3. 8. A concentrate according to claim 7, wherein the weight ratio of (a) to (b) plus (c) is in the range of 1:1.2 to 1:2.5. 9. A concentrate according to any one of the preceding claims, wherein the polyamine is one or more alkylene polyamines, cyclic alkylene polyamines, acyclic alkylene polyamines or a mixture of two or more of the above substances, each alkylene group having 1 to 10 carbon atoms and the acyclic hydrocarbyl substituent is a polyalkylene having 64 to 80 carbon atoms and the non-hydrotreated poly-α-olefin has a viscosity of 10 cSt at 100ºC. 10. A concentrate according to claim 9, wherein the polyamine is triethylenetetramine or a combination of ethylenepolyamines close to triethylenetetramine. 11. A concentrate according to any preceding claim, containing a mineral oil having a volatility of 50% or less and in which the ratio of mineral oil to poly-α-olefin is in the range of 3:1 to 0.5:1. 12. A motor fuel containing (i) a major amount of hydrocarbons in the boiling range of gasoline or mixtures of hydrocarbon and oxygenated substances or oxygenated substances and (ii) a minor but effective amount of the components of a fuel additive concentrate according to any one of claims 1 to 11. 13. A method for controlling octane demand increase in internal combustion engines (gasoline engines) or for reducing induction system deposits in internal combustion engines (gasoline engines) which comprises providing for use as a fuel composition a major amount of an unleaded gasoline and a minor but effective amount of an octane demand increase controlling mixture or an induction system deposit reducing mixture comprising the following components: (a) the reaction product of (i) polyamine and (ii) at least one acyclic hydrocarbyl substituted succinic acid as acylating agent; (b) a non-hydrotreated liquid poly-α-olefin oligomer having a volatility of 50% or less and (c) optionally, a mineral oil having a viscosity index of less than about 90 and a volatility of 50% or less, such volatility being expressed as a weight percent of substance lost, based on the total initial weight of the material tested, when such material is heated in a 250 ml round bottom flask to 300°C for one hour with stirring at 150 rpm, while the free space above the material in the flask is purged with 7.5 l of air/h, thereby effectively controlling the increase in the octane requirement of an internal combustion engine. 14. A process according to claim 13, wherein the components of the mixture are as defined in claims 2 to 11.