Cross-Reference to Related Applications

This application claims the benefit of U.S. Provisional Application No. 61/864,784, filed on August 12, 2013, which is incorporated herein by reference.

Background of the Invention

Under ideal conditions, normal combustion in a conventional spark-ignited engine occurs when a mixture of fuel and air is ignited within the combustion chamber inside the cylinder by the production of a spark originating from a spark plug. Such normal combustion is generally characterized by the expansion of the flame front across the combustion chamber in an orderly and controlled manner.

However, in some instances, the fuel/air mixture may be prematurely ignited by an ignition source prior to the spark plug firing, thereby resulting in a phenomenon known as pre-ignition. Pre-ignition is undesirable as it typically results in the presence of greatly increased temperatures and pressures within the combustion chamber, which may have a significant, negative impact on the overall efficiency and performance of an engine. Pre- ignition may cause damage to the cylinders, pistons and valves in the engine and in some instances may even culminate in engine failure.

Recently, low-speed pre-ignition ("LSPi") has been recognized amongst many original equipment manufacturers ("OEMs") as a potential problem for highly boosted, downsized spark-ignited engines. Contrary to the pre-ignition phenomenon observed in the late 50' s at high speeds, LSPI typically occurs at low speeds and high loads, ^r I¾e occurrence of LSPI may ultimately lead to so-called "monster knock" or "mega-knock" where potentially devastating pressure waves can result in severe damage to the piston and/or cylinder. As such, any technology that can mitigate the risk of pre-ignition, including LSPI, would be highly desirable.

Summary of the Invention

The present disclosure generally relates to methods for modifying auto-ignition properties of a base oil or lubricant composition. The present disclosure also provides associated lubricant compositions comprising an ignition delay additive.

The present disclosure provides methods of increasing the ignition delay time of a base oil or a lubricant composition comprising: providing the base oil or the lubricant composition having a first ignition delay time; adding an ignition delay additive to the base oil or the lubricant composition so as to form a second lubricant composition having a second ignition delay time, wherein the second ignition delay time is greater than the first ignition delay time.

The present disclosure additionally provides methods of introducing a lubricant composition comprising an ignition delay additive into a crankcase of a spark-ignited engine.

The present disclosure further provides lubricant compositions for use in the crankcase of an engine comprising: a base oil and an ignition delay additive selected from the group consisting of: diphenylamine, m-Anisidine, 4-Ffuoroaniline, N-methyl aniline, 4-Ethylaniline, 2,4,6-Trimethylphenol, p-Cresol, m-toluidine, 1,2,3,4-Tetrahydroquinoline, derivatives thereof, and mixtures thereof,

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

Description of the Drawings

Some specific example embodiments of the disclosure may be understood by referring, in part, to the following description and the accompanying drawings.

Figures 1 and 2 are graphs depicting pressure vs. time curves for the Fuel Ignition Analyzer,

Figures 3 and 4 are graphs depicting ignition delay times for various lubricant compositions.

Figures 5 and 6 axe graphs depicting the position of maximum heat release (PMR) for various lubricant compositions.

Figures 7 and 8 are graphs depicting the maximum heat release rate (MHRR) for various lubricant compositions.

While the present disclosure is susceptible to various modifications and alternative forms, specific example embodiments have been shown in the figures and are herein described in more detail. It should be understood, however, that the description of specific example embodiments is not intended to limit the invention to the particular forms disclosed, but on the contrary, this disclosure is to cover all modifications and equivalents as illustrated, in part, by the appended claims. Detailed Description

Traditional lubricant compositions used in the crankcase of an internal combustion engine tend to have a relatively low ignition delay time (relative to the fuel components) due, at least in part, to their high molecular weight and long-chained molecular structure. In general, the ignition delay time of a fluid, or fluid/air mixture, may be used as a measure of its reactivity or as a means to indicate the amount of time necessary for it to auto-ignite at a given pressure, temperature and equivalence ratio.

While the exact causes of LSPI are currently unknown, one theory is that if a lubricant composition haying a low ignition delay time (relative to the fuel components), enters the combustion chamber of an engine, for example, by being flicked into it by the top ring, by reverse blow-by, etc, the presence of that lubricant composition in the combustion chamber could contribute to the likelihood that pre-ignition may occur.

Accordingly, the disclosure herein provides methods of modifying the auto-ignition properties of a base oil or lubricant composition by adding an ignition delay additive thereto. By adding an ignition delay additive to the base oil or lubricant composition, the auto-ignition properties may be modified such that the lubricant composition has an increased ignition delay time, thereby mitigating the risk of pre-ignition. Additionally, the present disclosure provides lubricant compositions comprising an ignition delay additive. As used herein, the term "ignition delay additive" refers to a compound that when added to a base oil or a lubricant composition increases the ignition delay time of the base oil or lubricant composition to which it was added. Similarly, the term "ignition delay time" refers to the period of time between the start of injection and onset of combustion {see Figure 1 and Energy Institutes IP Standards Method IP 541/06).

The ignition delay time (ID) of a lubricant composition comprising an ignition delay additive may be measured using any suitable method, so long as the ID for the composition with the ignition delay additive is compared with the ID for the same composition but without the ignition delay additive present, and both ID values are obtained using the same method and under the same operating conditions, This is because different measurement methods can yield different values of ID even for the same lubricant composition. One example of a suitable method for measuring ignition delay time utilizes a Fuel Ignition Analyzer (FI A), as discussed in the examples herein. When using a HA to measure the ignition delay time of a lubricant composition, the period of time between the start of injection and onset of combustion is typically determined by injection needle movement and pressure sensors in the instrument.

Lubricant compositions of the present disclosure generally comprise a base oil and an ignition delay additive, and should be suitable for use in a spark-ignited internal combustion engine. In some embodiments, the lubricant compositions disclosed herein may be particularly useful in a turbocharged spark-ignited engine, more particularly a turbocharged spark-ignited engine which operates, or may operate, or is intended to operate, with an inlet pressure of at least I bar.

A. Base Oil

There are no particular limitations regarding the base oil used in the lubricating compositions, and various conventional mineral oils, synthetic oils as well as any base oil which belongs to Group I, Group II, Group III, Group IV, Group V and so on of the API (American Petroleum Institute) base oil categories, may be conveniently used, provided that the requirements in respect of the lubricant compositions according to the present disclosure are met. Furthermore, the base oil may conveniently comprise mixtures of one or more mineral oils and/or one or more synthetic oils; thus, the term "base oil" may refer to a mixture comprising more than one base oil.

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

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

Paraffinic base oils have higher VI (generally >95) and a high pour point. Such base oils are produced from feedstocks rich in paraffins, and are used for lubricants in which VI and oxidation stability are important.

Fisclier-Tropsch derived base oils may be used as the base oil. By the term "Fischer- Tropsch derived" is meant that a base oil is, or is derived from, a synthesis product of a Fischer-Tropsch process. A Fischer-Tropsch derived base oil may also be referred to as a

GTL (Gas-To-Liquids) base oil. Suitable Fischer-Tropsch derived base oils that may be conveniently used as the base oil are those as for example disclosed in EP 0 776 959, EP 0 668 342, WO 97/21788, WO 00/15736, WO 00/14188, WO 00/14187, WO 00/14183, WO 00/1 179, WO 00/08115, WO 99/41332, EP 1 029 029, WO 01/18156 and WO 01/57166.

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

Poly-alpha olefin base oils (PAOs) and their manufacture are well known in the art. Suitable poly-alpha olefin base oils that may be used include those derived from linear C ₂ to C32, preferably C _& to C _½ , alpha olefins. Particularly preferred feedstocks for said poly-alpha olefins are 1-octene, 1-decene, 1-dodecene and 1-tetradecene.

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

It is further preferred that the base oil contains less than 1.0 wt. %, preferably less than

0.03 wt. % of sulfur, calculated as elemental sulfur and measured according to ASTM D2622, ASTM D4294, ASTM D4927 or ASTM D3120.

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

Preferably, the base oil preferably has a kinematic viscosity at 100°C of at least 2.5 mm ² ./s (according to ASTM D445), preferably at least 3 mm ² /s. In some embodiments, the base oil has a kinematic viscosity at 100°C of between 3.0 and 4.5 mm ² /s.

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

B. Ignition Delay Additives

The lubricant compositions further comprise an ignition delay additive. Suitable ignition delay additives may include any compound that, when added to a base oil or a lubricant composition, increases the ignition delay time of the base oil or lubricant composition to which it was added. Examples of suitable ignition delay additives include, but are not limited to, dipheny! amine, m-Anisidine, 4-Fiuoroaniiine, N-methyl aniline ("NMA"), 4-Ethylaniline, 2,4,6-Trimethylphenoi, p-Cresol, m-toluidine, 1 ,2 , 3 ,4-Tetrahydroquinoiine ("THQ"), derivatives thereof, and mixtures thereof. Particularly preferred ignition delay additives may include NMA and THQ.

Preferably, the ignition delay additive is present in an amount in the range of from 0.01 -10 wt. %, more preferably in an amount in the range of from 0.01-2 wt. %, and most preferably in an amount in the range of from 0-.5 wt. %, based on the total weight of the lubricant composition.

C. Other Additives

Additionally, the lubricant compositions may further comprise additional additives such as anti-oxidants, anti-wear additives, detergents, dispersants, friction modifiers, viscosity index improvers, pour point depressants, corrosion inhibitors, anti-foam agents, extreme pressure additives, metal passivators and seal fix/seal compatibility agents.

Examples of suitable anti-oxidants include, but are not limited to, aminic antioxidants, phenolic antioxidants, and mixtures thereof, Examples of aminic antioxidants which may be conveniently used include alkylated diphenylamines, phenyl- -naphthyiamines, phenyl- β- naphthylamines and alkylated a-naphthylamines.

Preferred aminic antioxidants include dialkyldiphenylamines such as p,p'-dioctyl- diphenylamine, p,p'-di- -methylbenzyl-diphenylamine and N-p-butylphenyl-N-p'- octylphenylamine, monoaJkyldiphenylamines such as mono-t-butyldiphenylamine and mono- octyldiphenylamine, bis(dialkylphenyl)amines such as di-(2,4-diethylphenyl)amine and di(2- eihyl-4-nonylphenyl)amine, alkylphenyl-1 -naphthylamines such as octylphenyl-1- naphthylamine and n-t-dodecy phenyl-1 -naphthylamine, 1-naphthylamine, arylnaphthylamines such as phenyl-l-naphthylamine, phenyl-2-naphthylamine, N- hexylphenyl-2-naphthylamine and N-octylphenyl-2-naphthylamine, phenylenediamines such as N,N'-diisopropyl-p-phenylenediamine and N,N'-diphenyl-p-phenylenediamine, and phenothiazines such as phenothiazine and 3,7-dioctylphenothiazine.

Preferred aminic antioxidants include those available under the following trade designations: "Sonoflex OD-3" (ex. Seiko Kagaku Co.), "Irganox L-57" (ex. Ciba Specialty- Chemicals Co.) and phenothiazine (ex. Hodogaya Kagaku Co.).

Examples of phenolic antioxidants which may be conveniently used include C7-C9 branched alkyl esters of 3,5-bis(l,l-dimethyl-ethyl)-4-hydroxy-benzenepropanoic acid, 2-t- butylphenol, 2-t-butyl-4-niethylphenol, 2-t-butyl-5-methylphenol, 2,4-di-t-butylphenol, 2,4- dimethyl-6-t-butylphenol, 2-t-butyl-4-methoxyphenol, 3-t-butyl-4-methoxyphenol, 2,5-di-t- butylhydroquinone, 2,6-di-t-butyl-4-alkylphenols such as 2,6-di-t-butylphenol, 2,6-di-t-butyl- 4- methylphenol and 2,6-di-t-butyl-4-ethylphenol, 2,6-di-t-butyI-4-alkoxyphenols such as 2,6- di-t-butyl-4-methoxyphenol and 2,6-di-t-butyl-4-ethoxyphenol, 3,5-di-t-butyl-4- hydroxybeiizylmercaptooctylacetate, alkyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionates such as n-octadecyl-3-(3,5-di-t-butyl-4-hydiOxyphenj'l)pfopionate, n-butyl-3-(3,5-di-t-butyl- 4-hydroxyphenyl)propionate and 2'-eihylhexyl-3-(3,5-di-t-butyl-4-hydroxy henyl)propionat.e, 2,6-d-t-butyl- -dimethylamiiio-p-cresol, 2,2'-metb.yleiiebis(4-al] yl-6-t-butylphenol) such as 2,2'-niethylenebis(4-niethyl-6-i-butylphenol, and 2,2-methylenebis(4-ethyl-6-t-butylphenol), bisphenols such as 4,4'-butylidenebis(3-me{hyl-6-t-butylphenol, 4,4'-methylenebis(2,6-di-t- butylphenol), 4,4'-bis(2,6-di-t-butylphenol), 2,2-(di-p-hydroxyphenyl)propane, 2,2-bis(3,5-di- t-butyl-4-hydroxyphenyl)propane, 4,4'-cyclohexylidenebis(2,6-t-butylphenol), hexainethyleneglycol-bis[3-(3,5-di-t-butyl-4-hydroxyphenyl)p ropionate],

triethyleneglycolbis [3 - (3 - t-butyl-4 - hydroxy ^■ 5 -methylphenyl)propionate j , 2,2' ^■ thio - [diethyl-3- (3 ,5 -di- -t-butyl - 4 -hydroxyphenyl)propionate] , 3 , 9- bis { 1 , 1 -dimethyl-2- [3 - (3 - t ^■ butyl-4-hydroxy ^■ ·

5- methylphenyl)propionyloxy]ethyl}2,4,8,10-te{raoxaspiro[5,5]u ndecane, 4,4'-thiobis(3- rneibyi-6-t-butylphenol) and 2,2'~i.hiobis(4,6-di-t-bui.ylresorcinol), polyphenols such as

methyI-4-hydi xy-5-t-butylphenyl)butane, l,3,5-trimethyl-2,4,6-tris(3,5-di-t-butyl-4- hydroxybenzyl)benzene, bis-[3,3'-bis(4'-hydroxy-3'-t-butylphenyl)butyric acidjglycol ester, 2- (3^5'~di -butyί-4-hydro y enyi)rnethyί-4-(2 4''-di

butylphenol and 2,6-bis(2'-hydroxy~3'-t-butyl-5'-methylbenzyl)-4-metl ylphenoi, and p-t- butylphenol - formaldehyde condensates and p-t-butylphenol - acetaldehyde condensates.

Examples of suitable phenolic antioxidants include those which are commercially available under the following trade designations: "Irganox L-135" (ex, Ciba Specialty Chemicals Co.), "Yoshinox SS" (ex. Yoshitomi Seiyaku Co.), "Antage W-400" (ex. Kawagucbi agaku Co.), "Antage W-500" (ex. Kawaguchi Kagaku Co.), "Antage W-3()0" (ex. Kawaguchi Kagaku Co.), "Irganox L109" (ex. Ciba Speciality Chemicals Co.), "Tominox 917" (ex. Yoshitomi Seiyaku Co.), "Irganox LI 15" (ex. Ciba Speciality Chemicals Co.), "Sumilizer GA80" (ex. Sumitomo Kagaku), "Antage RC" (ex. Kawagucbi Kagaku Co.), "Irganox LI 01" (ex. Ciba Speciality Chemicals Co.), "Yoshinox 930" (ex. Yoshitomi Seiyaku Co.).

In a preferred embodiment, antioxidants are present in an amount in the range of from 0.1 to 5.0 wt. %, more preferably in an amount in the range of from 0.3 to 3.0 wt. %, and most preferably in an amount in the range of from 0,5 to 1.5 wt. %, based on the total weight of the lubricant composition.

Anti-wear additives that may be conveniently used include zinc- containing compounds such as zinc dithiophosphate compounds selected from zinc dialkyl-, diaryl- and/or alkylaryi- dithiophosphates, molybdenum-containing compounds, boron-containing compounds and ashless anti-wear additives such as substituted or unsubstituted thiophosphoric acids, and salts thereof.

Zinc dithiophosphate is a well known additive in the art, and may be conveniently represented by general formula ΪΙ;

s s wherein R ² to R ⁵ may be the same or different and are each a primary alkyl group containing from 1 to 20 carbon atoms preferably from 3 to 12 carbon atoms, a secondary alkyl group containing from 3 to 20 carbon atoms, preferably from 3 to 12 carbon atoms, an aryl group or an aryl group substituted with an alkyl group, said alkyl substituent containing from 1 to 20 carbon atoms preferably 3 to 18 carbon atoms.

Zinc dithiophosphate compounds in which R ^z to R ³ are ail different from each other can be used alone or in admixture with zinc dithiophosphate compounds in which R ^a to R ⁵ are all the same.

Examples of suitable zinc dithiophosphates include those which are commercially available under the following trade designations: "Lz 1097", "Lz 1395", "Lz 677A", "Lz 1095", "Lz 1370", "Lz 1371", and "Lz 1373" (ex. Lubrizol Corporation); "OLOA 267", "OLOA 269R", "OLOA 260" and "OLOA 262" (ex. Chevron Oronite); and "IIITEC 7197" and "HiTEC 7169" (ex. Afton Chemical).

Examples of molybdenum-containing compounds may conveniently include molybdenum dithiocarbamates, trinuclear molybdenum compounds, for example as described in WO 98/26030, sulphides of molybdenum and molybdenum dithiophosphate. Boron-containing compounds that may be conveniently used include borate esters, borated fatty amines, borated epoxides, alkali metal (or mixed alkali metal or alkaline earth metal) borates and borated overbased metal salts.

The lubricant compositions may generally comprise in the range of from 0,4 to 1.2 wt. % of an anti-wear additive, based on the total weight of the lubricant composition,

Typical detergents that may be used in the lubricating compositions include one or more salicylate and/or phenate and/or sulphonate detergents. However, as metal organic and inorganic base salts which are used as detergents can contribute to the sulfated ash content of a lubricant composition, in a preferred embodiment, the amounts of such additives are minimized. Furthermore, in order to maintain a low sulphur level, salicylate detergents are preferred.

In order to maintain the total sulfated ash content of the lubricant composition at a level of preferably not greater than 2.0 wt, %, more preferably at a level of not greater than 1.0 wt. % and most preferably at a level of not greater than 0.8 wt, %, based on the total weight of the lubricant composition, said detergents are preferably used in amounts in the range of 0.05 to 20.0 wt. %, more preferably from 1.0 to 10.0 wt. % and most preferably in the range of from 2.0 to 5.0 wt. %, based on die total weight of the lubricant composition.

Furthermore, the detergents may independently have a TBN (total base number) value in the range of from 10 to 500 mg.KOH/g, more preferably in the range of from 30 to 350 mg.KOH/g and most preferably in the range of from 50 to 300 mg.KOH/g, as measured by ISO 3771.

The lubricant compositions may additionally contain an ash-free dispersant which is preferably admixed in an amount in the range of from 5 to 15 wt. %, based on the total weight of the lubricant composition,

Examples of ash-free dispersants which may be used include the polyalkenyl succinimides and polyalkenyl succininic acid esters disclosed in Japanese Patent Nos. 1367796, 1667140, 1302811 and 1743435. Preferred dispersants include borated succinimides,

Examples of viscosity index improvers which may be conveniently used in the lubricant compositions include the styrene-butadiene copolymers, styrene-isoprene stellate copolymers and the polymethacrylate copolymer and ethylene-propylene copolymers. Such viscosity index improvers may be conveniently employed in an amount in the range of from 1 to 20 wt. %, based on the total weight of the lubricant composition. Polymcthacryki.es may be conveniently employed in the lubricant compositions as effective pour point depressants. For corrosion inhibitors, it is possible to use alkenyi succinic acid or ester moieties thereof, be zotriazoie-based compounds and thiodiazole -based compounds .

Compounds such as polysiSoxanes, dimethyl polycyclohexane and poSyacryiates may be conveniently used in the lubricant compositions as anti-foam agents.

Compounds which may be conveniently used in the lubricant compositions as seal fix or seal compatibility agents include, for example, commercially available aromatic esters.

The lubricant compositions may be conveniently prepared using conventional formulation techniques by admixing a base oil or lubricant with the ignition delay additive and. if desired, one or more additives.

The disclosure herein also provides methods of modifying the auto-ignition properties of a base oil or lubricant composition by adding an ignition delay additive thereto, Similarly, in certain embodiments, the disclosure herein provides methods of increasing the ignition delay time of a base oil or a lubricant composition by adding an ignition delay additive to the base oil or lubricant composition.

In another aspect, the present disclosure also provides methods that comprise introducing a lubricant composition comprising an ignition delay additive into a crankcase of a spark-ignited engine. In certain embodiments, the engine may be a turbocharged spark- ignited engine.

The disclosure herein further provides the u e of a lubricating composition comprising a base oil and an ignition delay additive in the crankcase of a spark-ignited engine for reducing pre-i gnition.

The level of occurrence of pre-ignition in a spark-ignited engine may be assessed using any suitable method. In general, such a method may involve running a spark-ignited engine using the relevant lubricant composition, and monitoring changes in engine pressure during its combustion cycles, i.e., changes in pressure versus crank angle. A pre-ignition event will result in an increase in engine pressure before sparking: this may occur during some engine cycles but not others. Instead, or in addition to, changes in engine performance may be monitored, for example by maximum attainable brake torque, engine speed, intake pressure and/or exhaust gas temperature. Instead, or in addition to, a suitably experienced driver may test-drive a vehicle which is driven by the spark-ignited engine, to assess the effects of the lubricant composition on, for example, the degree of engine knock or other aspects of engine performance. Instead, or in addition to, levels of engine damage due to pre-ignition, for example due to the associated engine knock, may be monitored over a period of time during which the spark-ignited engine is running using the relevant lubricant composition.

A reduction in the occurrence of pre-ignition may be a reduction in the rate at which pre-ignition events occur within the engine, and/or in the severity of the pre-ignition events which occur (for example, the degree pressure change which they cause). It may be manifested by a reduction in one or more of the effects which pre-ignition can have on engine performance, for example impairment of brake torque or inhibition of engine speed. It may be manifested by a reduction in the amount or severity of engine knock, in particular by a reduction in, or elimination of, "mega knock".

Since pre-ignition, particularly if it occurs frequently, can cause significant engine damage, the lubricant compositions disclosed herein may also be used for the purpose of reducing engine damage and/or for the purpose of increasing engine longevity.

The methods and lubricant compositions herein may be used to achieve any degree of reduction in the occurrence of pre-ignition in the engine, including reduction to zero (i.e., eliminating pre-ignition). It may be used to achieve any degree of reduction in a side effect of pre-ignition, for example engine damage. It may be used for the purpose of achieving a desired target level of occurrence or side effect.

To facilitate a better understanding of the present invention, the following examples of certain aspects of some embodiments are given. In no way should the following examples be read to limit, or define, the entire scope of the invention.

EXAMPLES

Lubricant compositions comprising a base oil and an ignition delay additive were formulated as indicated in Tables I and 2, All formulations were manufactured by blending together the base oil/lubricant and the ignition delay additive using conventional mixing techniques.

The base oil used in the formulations contained in Table 1 was a binary blend of a first polvalphaolefin base oil having a kinematic viscosity of 40 mm ² /s at 100° C (PAO 40) and a second polyalphaoSefin base oil having a kinematic viscosity of 5 mm s at 100° C (PAO 5), as measured by ASTM D445.

The formulations in Table 2 contained "Shell Helix Ultra 5W/30 A3/B4" as the lubricant, which is commercially available from the Royal Dutch Shell Group of Companies. The PAC) blend used in the formulations of Table 1 was chosen to have approximately the same viscometrics as the Helix lubricant used in the formulations of Table 2.

Where possible, die ignition delay additives were blended into the formulations at a

2% (mass) level, but in some cases this was not possible as the additive dropped out of solution.

The formulations were all subjected to Fuel Ignition Analyzer (FIA) testing using a FIA manufactured by Fuel Tech to determine the following three parameters:

Ignition Delay Time (ID) - measured as the time taken from start of injection of the composition to a recovery in pressure of 0.01 of the final maximum pressure increase;

Position of Maximum Rate of Heat Release (PMR) - measured as the position of the peak of the heat release rate curve (or the position of the maximum gradient of the Pressure vs time curve - see Figure 1); and

Maximum Heat Release Rate (MHRR) - measured as the height of the peak in the Heat Release curve (or the maximum gradient of the Pressure vs time curve - see Figure 2).

FIA testing consisted of direct injection of the sample formulation into a heated, pressurized constant volume combustion chamber. The temperature and pressure of the chamber was set at 420° C and 37 bar, and the injection temperature was set to 125° C. Although FIA testing is normally used to test the ignition qualities of marine and residual fuels, its use herein is appropriate as it presents a representative system that emulates the in- cylinder conditions to be found in a modern boosted gasoline engine.

The ID, PMR and MHRR results for the formulations are included in Table 1 (for PAO blends) and Table 2 (for Helix blends).

Table 1 - PAO blends

Table 2 - Helix blends Discussion

Tables 1 and 2 show that the addition of an ignition delay additive to a base oil or a lubricant leads to an increase in ignition delay time. These results are also depicted graphically in Figures 3 and 4, respectively.

Similarly, Tables 1 and 2 show that the addition of an ignition delay additive to a base oil or a lubricant leads to an increase in the time (position) at which the maximum heat release occurs. These results are also depicted graphically in Figures 5 and 6, respectively.

Furthermore, Tables 1 and 2 show that the addition of an ignition delay additive to a base oil or a lubricant leads to a decrease in the maximum rate of heat release. These results are also depicted graphically in Figures 7 and 8, respectively.

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