Field of the Invention

The present invention relates to an engine oil for motor vehicles (a lubricating oil composition for

internal combustion engines) and, more specifically, it relates to an engine oil for motor vehicles having

outstanding friction reducing performance, engine

cleaning performance and oxidation stabilizing

performance .

Background of the Invention

In terms of the performance classification of motor vehicle engine oils, the standards primarily established by the API (American Petroleum Institute) and the ILSAC (International Lubricants Standardization and Approval Committee) set up by Japanese/US motor vehicle

manufacturers are recognized as being the engine oil standards which most anticipate market needs. In this respect, recently, the API-SN and ILSAC GF-5 standards have been enacted from the point of view of improving fuel economy and sustainability, improving engine

protection performance, and improving exhaust emission control equipment protection performance. The required properties to achieve such performance levels are diverse, and encompass the viscosity grade, gelling index,

oxidation stability, piston cleaning property, wear prevention, engine cleaning property, valve train system wear prevention, bearing corrosion prevention, fuel efficiency, aeration of the oil used, catalyst poisoning, wear prevention, volatility, suppression of high

temperature deposits, suppression of filter blockage, defoaming, oil low temperature viscosity, shear stability, homogeneity and mixability, low temperature corrosion prevention, complex fuel compatibility, and rubber seal compatibility, etc., so numerous additives are

incorporated, with the result that interactions between these is becoming a problem. While a given additive is effective in terms of a single property, it may have a minus effect in terms of another, so blending techniques are becoming increasingly difficult. In particular, friction modifiers are currently used to improve fuel efficiency, but these compounds are highly active, and it is known that they have adverse effects on the cleaning properties, the occurrence of deposits, and oxidation stability, etc.

As friction modifiers, glyceride compounds which contribute to the friction lowering performance are commonly used as an ashless type of friction modifier since they do not contain a metal, but when added in the amount required to achieve fuel economy there are

problems in terms of the engine cleaning property and oxidation stability, so there has been the difficulty that they cannot be added in adequate quantities.

Additionally, in terms of wear prevention and oxidation prevention, zinc dialkyl-dithiophosphates (ZDTPs) have been used hitherto as the most preferred additives.

However, the phosphorus in a zinc dialkyl-dithiophosphate

(ZDTP) is a factor causing deterioration in the

automotive catalyst environment so, if such a compound is used in a large amount, it will be difficult to meet the GF-5 standard and future anticipated requirements to lower the phosphorus content. Hence, there is a demand for an engine oil which meets the GF-5 specification and can respond to the stricter specifications anticipated in the future, by manifesting properties such as wear resistance and oxidation stability performance while still having a low phosphorus content. Thus, in JP-A- 2005-002214, there has been proposed a lubricating oil for an internal combustion engine which can exhibit the performance required in terms of wear resistance and oxidation stability, etc., while satisfying the

requirements of the GF-5 standard.

However, the novel effective component described in JP-A-2005-002214 is also a phosphorus-containing compound, so it will not necessarily be able to fully meet the GF-5 standard requirements of a low-phosphorus type

lubricating oil and the requirements which are expected in the future. Hence, the present invention addresses the problem of providing a means for achieving

outstanding friction lowering performance, engine

cleaning performance and oxidation stability performance even in the case where the amount of phosphorus- containing component is lowered in an engine oil for motor vehicles.

As a result of screening diverse combinations of non phosphorus-based components known to be additives, the present inventors have discovered that by the combination of a specified component with another specified component there is obtained a combination which enables outstanding friction lowering performance, engine cleaning

performance and oxidation stability performance to be realized, and it is on this discovery that the present invention is based.

Summary of the Invention

According to the present invention there is provided an engine oil for motor vehicles characterized in that it comprises glycerin 1-oleate, which is represented by the following formula (1) : [Formula (1) ] :

R1-COO-CH ₂

I

I

CH ₂ OH

(wherein Rl is the oleyl group) , and one or more

monoalkyl- or monoalkenyl-amine ethylene oxide adducts represented by the following formula (2) :

[Formula (2) ] :

(wherein R is a Cs to C ₂₂ hydrocarbyl group, and n and m are each independently 1 or 2) .

In accordance with the present invention, by the joint presence of glycerin 1-oleate (glyceryl monooleate, GMO) and a monoalkyl- or monoalkenyl-amine ethylene oxide adduct of specified structure, there is the effect that it is possible to provide an engine oil having

outstanding friction lowering performance, engine

cleaning performance and oxidation stability performance while satisfying the GF-5 standard (and still more demanding standards anticipated in the future) . Now, at this point in time, the present invention is particularly ideal as a motor vehicle engine oil composition according to the latest API-SN and ILSAC GF-5 specifications, but there is no particular restriction to the engine oil compositions of these specifications.

Detailed Description of the Invention

As the base oil (base stock) for the engine oil relating to this mode of the invention, it is possible to employ the mineral oils and synthetic oils used in normal lubricating oils. In particular, the base oils belonging to Group 1, Group 2, Group 3 and Group 4, etc., in the API (American Petroleum Institute) base oil categories can be used on their own or as mixtures.

The Group 1 base oils include the paraffinic mineral oils obtained by, for example, applying a suitable combination of purification means such as solvent

refining, hydro-refining and dewaxing, etc., to the lubricating oil fraction obtained by the atmospheric distillation of crude oil. The viscosity index is preferably 80-120 and more preferably 95-110. The kinematic viscosity at 100°C is preferably 2 to 32 mm ² /s, and more preferably 3 to 12 mm ² /s. The total nitrogen component should be less than 50 ppm, and preferably less than 25 ppm. Furthermore, the aniline point is

preferably between 80 and 150°C, and more preferably between 90 and 120°C.

The Group 2 base oils include paraffinic mineral oils obtained by, for example, applying a suitable combination of purification means such as hydro-cracking and dewaxing, etc., to the lubricating oil fraction obtained by the atmospheric distillation of crude oil. Group 2 base oils obtained by hydro-refining methods such as the Gulf Co. method have a total sulphur component content of less than 10 ppm and an aromatics content of no more than 5%. The viscosity of these base oils is not particularly restricted but the viscosity index is preferably 90-125, and more preferably 100-120. The kinematic viscosity at 100°C is preferably 2 to 32 mm ² /s, and more preferably 3 to 12 mm ² /s. The total sulphur content is preferably less than 300 ppm, more preferably less than 100 ppm, and in particular less than 10 ppm. The total nitrogen component is preferably less than

10 ppm, and more preferably less than 1 ppm. Furthermore, the aniline point is preferably between 80 and 150°C, and more preferably between 100 and 135°C.

Preferred Group 3 base oils are, for example, the paraffinic mineral oils produced by subjecting the

lubricating oil fraction obtained by the atmospheric distillation of crude oil to high level hydro-refining, the base oils produced by the Isodewaxing process where the wax formed in the dewaxing process is converted to isoparaffins , and the base oils produced by the Mobil Wax Isomerization process. The viscosity of these base oils is not particularly restricted but the viscosity index is preferably 120-150, and more preferably 120-145. The kinematic viscosity at 100°C is preferably 2 to 32 mm ² /s, and more preferably 3 to 12 mm ² /s. The total sulphur content is preferably 0 to 100 ppm, and more preferably less than 10 ppm. The total nitrogen component is

preferably less than 10 ppm, and more preferably less than 1 ppm. Furthermore, the aniline point is preferably between 80 and 150°C, and more preferably between 110 and 135°C.

Examples of synthetic oils are polyolefins and, optionally, there may be used alkylbenzene,

alkylnaphthalene or ester mixtures, etc.

The above polyolefins include various types of olefin polymer and their hydrogenated products. While any olefin may be employed, examples are ethylene,

propylene, butene, and a-olefins with five or more

carbons. In producing the polyolefin, a single such olefin may be used on its own or combinations of two or more may be employed. In particular, the polyolefins referred to as poly a-olefins (PAOs) are preferred, and these are Group 4 base oils. The viscosity of these synthetic base oils is not particularly restricted but the kinematic viscosity at 100°C is preferably 2 to

32 mm ² /s, and more preferably 3 to 12 mm ² /s. Examples of the esters are diesters synthesized from monohydric alcohols and dibasic acids such as adipic acid, polyol esters synthesized from a monobasic acid and a polyhydric alcohol such as neopentyl glycol, trimethylolpropane, pentaerythritol or the like, and mixtures of these.

When compared to the mineral oil base oils produced from crude oil, the GTL (gas to liquid) oils synthesized from natural gas using a liquid fuel conversion technique employing the Fischer Tropsch method have an extremely low sulphur content and aromatic content, and the

proportion of paraffinic structure is extremely high, so they have outstanding oxidation stability, and the evaporation loss is extremely low. The viscosity

properties of the GTL base oils are not particularly restricted but, normally, the viscosity index is

preferably 120-180 and more preferably 120-150. The kinematic viscosity at 100°C is preferably 2 to 32 mm ² /s, and more preferably 3 to 12 mm ² /s. The total sulphur content in a normal example is preferably less than

10 ppm, and a total nitrogen content of less than 1 ppm is further preferred. As an example of a commercial such

GTL base oil product, there is Shell XHVI (registered trademark) .

The glycerin 1-oleate included as an indispensable component in the engine oil of the present invention is represented by the following formula (I) :

[Formula (I) ] : R1-COO-CH ₂

CHOH

CH ₂ OH

(wherein Rl is the oleyl group) .

The monoalkyl- or monoalkenyl-amine ethylene oxide adduct included as an indispensable component in the engine oil of the present invention is represented by the following formula (2) :

[Formula (2) ] :

(wherein R is a C8-22 hydrocarbyl group, and n and m are each independently 1 or 2) . The C8-22 hydrocarbyl group preferably has from 8 to 20 carbons, and specific

examples are alkyl groups such as the octyl group, nonyl group, decyl group, undecyl group, dodecyl group,

tridecyl group, tetradecyl group, pentadecyl group, hexadecyl group, heptadecyl group, octadecyl group, nonadecyl group and eicosyl group (these alkyl groups may be straight-chain or branched) , and alkenyl groups such as the octenyl group, nonenyl group, decenyl group, undecenyl group, dodecenyl group, tridecenyl group, tetradecenyl group, pentadecenyl group, hexadecenyl group, heptadecenyl group, octadecenyl group, nonadecenyl group and eicosenyl group (these alkenyl groups may be

straight-chain or branched; the double bond may be at any position; and they may be cis- or trans- isomers) . It is preferred that n and m here are both 1. Furthermore, the flash point (COC) is preferably at least 200°C. One such adduct may be employed or there may be used a mixture of two or more types.

Examples of metal-based cleaning agents which can be used in the engine oil of the present invention include alkaline earth metal sulphonates, alkaline earth metal phenates, alkaline earth metal salicylates, alkaline earth metal naphthenates , and the like. Examples of the alkaline earth metals are calcium and magnesium. These metal-based cleaning agents may be employed on their own or two or more may be used in combination. Normally, calcium or magnesium sulphonate, phenate or salicylate is preferably used. As the alkaline earth metal phenates, the alkaline earth metal salts of alkylphenols ,

alkylphenol sulphides or alkylphenol Mannich reaction products having a C4-30, and preferably a C6-18, straight- chain or branched alkyl group are preferably used, in particular the calcium salts. As the alkaline earth salicylate, the alkaline earth salts of an alkylsalicylic acid having a Ci-30, and preferably a C6-18 _/ straight-chain or branched alkyl group are preferably used, with the use of the magnesium salts and/or the calcium salts being particularly preferred. The base value of these can be selected in accordance with the objectives and type of lubricating oil.

Examples of the ashless dispersants which can be used in the engine oil of the present invention are those of the polybutenyl succinimide, polybutenyl succinamide, benzylamine and succinate ester types. These dispersants may also be borated. Polybutenyl succinimide is obtained from polybutene which is itself produced by the

polymerization of isobutene, or a mixture of 1-butene and isobutene, using a boron fluoride type catalyst or an aluminium chloride type catalyst, and there is normally included material with from 5 to 100 mol% vinylidene structure at the polybutene terminals. From the point of view of obtaining an outstanding sludge suppressing effect, it is preferred that there be included from 2 to 5, and in particular from 3 to 4, nitrogen atoms in the polyalkylene polyamine chain. Furthermore, as examples of the polybutenyl succinimide derivatives, there can be used the so-called modified succinimides formed by subjecting an aforesaid polybutenyl succinimide to the action of a boron compound such as boric acid, or an oxygen-containing organic compound such as an alcohol, aldehyde, ketone, alkylphenol, cyclic carbonate or organic acid, and then neutralizing or amidating some or all of the remaining amino groups and/or imino groups. In particular, the boron-containing alkenyl (or alkyl) succinimides obtained by reaction with a boron compound such as boric acid are excellent in terms of

heat/oxidation stability.

Zinc dithiophosphates (ZnDTPs) may be given as examples of the antiwear agents used in the engine oil of the present invention for conferring wear resistance and extreme pressure characteristics. Generally speaking, examples of ZnDTPs include zinc dialkyl dithiophosphates, zinc diaryl dithiophosphates, zinc aryl alkyl

dithiophosphates, and the like. The alkyl groups may be straight-chain or branched. With regard to the alkyl groups in the zinc dialkyl dithiophosphates, there may be used a zinc dialkyl dithiophosphate having primary or secondary C3-22 alkyl groups, or having alkylaryl groups substituted with C3-18 alkyl groups. Specific examples of the zinc dialkyl dithiophosphates are zinc dipropyl dithiophosphate, zinc dibutyl dithiophosphate, zinc dipentyl dithiophosphate, zinc dihexyl dithiophosphate, zinc diisopentyl dithiophosphate, zinc diethylhexyl dithiophosphate, zinc dioctyl dithiophosphate, zinc dinonyl dithiophosphate, zinc didecyl dithiophosphate, zinc didodecyl dithiophosphate, zinc dipropylphenyl dithiophosphate, zinc dipentylphenyl dithiophosphate, zinc dipropylmethylphenyl dithiophosphate, zinc

dinonylphenyl dithiophosphate, zinc didodecylphenyl dithiophosphate and the like.

Examples of the metal deactivators which can be used in the engine oil of the present invention are

benzotriazole derivatives such as benzotriazole and alkyl-tolutriazoles , and benzimidazole derivatives such as benzimidazoles and toluimidazoles . Furthermore, there are indazole derivatives such as toluindazoles ,

benzothiazole derivatives such as benzothiazoles and toluzothiazoles . Further examples are benzoxazole derivatives, thiadiazole derivatives, triazole

derivatives and the like.

Examples of the antioxidants which can be used in the engine oil of the present invention are amine type antioxidants and phenolic antioxidants. The amine type antioxidants include dialkyl-diphenylamines such as ρ,ρ'- dioctyl-diphenylamine (Nonflex OD-3; manufactured by the Seiko Chemical Co.), p, p' -di-a-methylbenzyl-diphenylamine and N-p-butylphenyl-N-p' -octylphenylamine,

monoalkyldiphenylamines such as mono-tert- butyldiphenylamine and monooctyldiphenylamine,

bis (dialkylphenyl ) amines such as di(2,4- diethylphenyl ) amine and di (2-ethyl-4-nonylphenyl) amine, alkylphenyl-l-naphthylamines such as octylphenyl-1- naphthylamine, and N- ert-dodecylphenyl-l-naphthylamine, arylnaphthylamines such as 1-naphthylamine, phenyl-1- 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, phenothiazine ( Phenothiazine ; manufactured by the

Hodogaya Chemical Co.) and 3, 7-dioctylphenothiazine . The phenolic antioxidants include 2- ert-butylphenol, 2-tert- butyl-4-methylphenol, 2- ert-butyl-5-methylphenol, 2,4- di- ert-butylphenol , 2, 4-dimethyl-6- ert-butylphenol, 2- tert-butyl-4-methoxyphenol , 3- ter -butyl-4 -methoxyphenol ,

2.5-di- ert-butylhydroquinone (Antage DBH; manufactured by the Kawaguchi Chemical Co.), 2 , 6-di- ert-butylphenol ,

2.6-di- ert-butyl-4-methylphenol, 2, 6-di- tert-butyl-4- ethylphenol and other such 2, 6-di- tert-butyl-4- alkylphenols , and 2, 6-di- ert-butyl-4-methoxyphenol, 2,6- di- ert-butyl-4-ethoxyphenol and other such 2,6-di-tert- butyl-4-alkoxyphenols . Further examples include 3,5-di- tert-butyl-4-hydroxybenzylmercapto-octyl acetate, n- octadecyl-3- (3, 5-di- ert-butyl-4-hydroxyphenyl) propionate (Yoshinox SS; manufactured by the Yoshitomi

Pharmaceutical Industrial Co.), n-dodecyl-3- ( 3 , 5-di- tert- butyl-4-hydroxyphenyl) propionate, 2' -ethylhexyl-3- (3,5- di- e -butyl-4 -hydroxyphenyl ) propionate,

benzenepropionic acid 3, 5-bis (1, 1-dimethyl-ethyl) -4- hydroxy-C7_9 branched alkyl ester (Irganox L135;

manufactured by the Ciba Speciality Chemicals Corp.) and other such alkyl-3- (3, 5-di- ert-butyl-4- hydroxyphenyl ) propionates , 2, 6-di- ert-butyl-a- dimethylamino-p-cresol , 2,2' -methylenebis (4-methyl-6- tert-butylphenol ) (Antage W-400; manufactured by the Kawaguchi Chemical Co.), 2, 2' -methylenebis (4-ethyl-6- tert-butylphenol ) (Antage W-500; manufactured by the Kawaguchi Chemical Co.) and other such 2,2'- methylenebis (4-alkyl-6- ert-butylphenol) compounds. Additionally, there are 4 , 4 ' -butylidenebis ( 3-methyl- 6- tert-butylphenol ) (Antage W-300; manufactured by the Kawaguchi Chemical Co.), 4 , 4 ' -methylenebis (2 , 6-di- tert- butylphenol) (Ionox 220AH; manufactured by Shell Japan Ltd), 4, 4' -bis (2, 6-di- ert-butylphenol) , 2,2-(di-p- hydroxyphenyl ) propane (Bisphenol A; manufactured by Shell Japan Ltd), 2, 2-bis (3, 5-di- ert-butyl-4- hydroxyphenyl ) propane, 4,4' -cyclohexylidenebi (2, 6- ert- butylphenol) , hexamethylene glycol bis [ 3- ( 3 , 5-di- tert- butyl-4-hydroxyphenyl) propionate] (Irganox L109;

manufactured by the Ciba Speciality Chemicals Corp.), triethylene glycol bis [3- (3- tert-butyl-4-hydroxy-5- methylphenyl ) propionate ] (Tominox 917; manufactured by the Yoshitomi Pharmaceutical Industrial Co.), 2, 2' -thio ^¬ lsdiethyl-3- (3, 5-di- ert-butyl-4-hydroxyphenyl) propionate] (Irganox L115; manufactured by the Ciba Speciality

Chemicals Corp.), 3, 9-bis { 1, l-dimethyl-2- [3- (3- tert- butyl-4-hydroxy-5- methylphenyl )propionyloxy] ethyl } 2 , 4 , 8 , 10- tetraoxaspiro [ 5 , 5 ] undecane (Sumilizer GA80; manufactured by the Sumitomo Chemical Co.), 4 , 4 ' -thiobis ( 3-methyl- 6- tert-butylphenol ) (Antage RC; manufactured by the

Kawaguchi Chemical Co.), 2 , 2 ' -thiobis ( 4 , 6-di- ert-butyl- resorcinol) and other such bisphenols. Again, there are tetrakis [methylene-3- (3, 5-di- ert-butyl-4- hydroxyphenyl ) propionate ] methane (Irganox L101;

manufactured by the Ciba Speciality Chemicals Corp.), 1, 1, 3-tris (2 -methyl-4 -hydroxy-5-tert-butylphenyl) butane (Yoshinox 930; manufactured by the Yoshitomi

Pharmaceutical Industrial Co.), 1 , 3 , 5-trimethyl-2 , 4 , 6- tris (3, 5-di- ert-butyl-4-hydroxybenzyl) benzene (Ionox 330; manufactured by Shell Japan Ltd), bis- [ 3, 3' -bis- (4 ' - hydroxy-3 '- ert-butylphenyl ) butyric acid] glycol ester, 2- (3' , 5' -di- ert-butyl-4-hydroxyphenyl) methyl-4- (2", 4"-di- tert-butyl-3"-hydroxyphenyl ) methyl- 6- ert-butylphenol , 2, 6-bis (2' -hydroxy-3' - ert-butyl-5 ' -methyl-benzyl) -4- methylphenol and other polyphenols, condensates of p- tert-butylphenol and formaldehyde, condensates of p-tert- butylphenol and acetaldehyde, and other phenol-aldehyde condensates, etc.

As examples of the viscosity index improvers which can be used in the engine oil of the present invention, there are non-dispersant type viscosity index improvers such as polymethacrylates , and ethylene-propylene

copolymers, styrene-diene copolymers, polyisobutylene, polystyrene and other olefin polymers, and also

dispersant type viscosity index improvers such as these same examples copolymerized with a nitrogen-containing monomer .

As examples of the defoamers which can be employed in the engine oil of the present invention, there are dimethylpolysiloxane, diethyl silicate, fluorosilicones and other such organosilicates , and polyalkyl acrylates and other such non-silicone type defoamers.

The glycerin 1-oleate content is preferably present in an amount of from 0.1 to 2.0 m.cL S S "6 based on the total mass of engine oil composition, with from 0.25 to

1.5 m.cLS S "6 further preferred, and from 0.5 to 1.2 mass i still further preferred.

The amount of the monoalkyl- or monoalkenyl-amine ethylene oxide adduct (the combined amount thereof, in the case where more than one is employed) is preferably in the range of from 0.1 to 2.0 m.cL S S "6 of the said one or more types thereof based on the total mass of engine oil composition, with from 0.2 to 1.5 m.cL S S "6 further preferred, and from 0.2 to 1.0 m.cL S S "6 still further preferred. Explanation is now provided of the preferred amounts of the other components optionally added to the engine oil composition relating to the present invention. First of all, the preferred amount of the antioxidant added, either singly or as a combination of more than one type, lies in the range 0.01 to 2 m.cL S S "6 based on the total mass of engine oil composition. The preferred amount of the metal deactivator added, either singly or as a

combination of more than one type, lies in the range 0.01 to 0.5 m.cL S S "6 based on the total mass of engine oil composition. The preferred amount of the antiwear agent (such as ZnDTP) added, either singly or as a combination of more than one type, lies in the range 0.01 to

0.10 m.cLsS"o # and more preferably in the range 0.05 to 0.08 m.cLsS"o # in terms of the amount of (P) based on the total mass of engine oil composition. Where the amount of phosphorus element contained in the ZnDTP in terms of the total weight of the engine oil is less than

0.01 m.cLsS"o # it is not possible to obtain adequate wear resistance, whereas with a high concentration exceeding

0.10 m.cL S S "6 there is increased poisoning of the motor vehicle exhaust gas cleaning catalyst. The preferred amount of the viscosity index improver added, either singly or as a combination of more than one type, lies in the range 0.05 to 20 m.cL S S "6 based on the total mass of engine oil composition. The preferred amount of the defoamer added, either singly or as a combination of more than one type, lies in the range 0.0001 to 0.01 mass i based on the total mass of engine oil composition. The preferred amount of the metal-based cleaning agent added, either singly or as a combination of more than one type, lies in the range 0.05 to 0.3 m.cL S S "6 based on the total mass of engine oil composition, with the range 0.1 to 0.2 m.cL S S "6 further preferred. The preferred amount of the ashless dispersant added, either singly or as a

combination of more than one type, lies in the range 0.01 to 0.3 m.cL S S "6 based on the total mass of engine oil composition.

Based on an engine oil composition identical to that of the engine oil composition of the present invention excepting that it does not contain the "glycerin 1-oleate and the "monoalkyl- or monoalkenyl-amine ethylene oxide adduct", it is preferred that there be at least a 5% coefficient of friction (reciprocating kinetic

coefficient of friction at 80°C) lowering (i.e.

improvement) effect, and it is further preferred that there be at least a 10% coefficient of friction

(reciprocating kinetic coefficient of friction at 80°C) lowering (i.e. improvement) effect. Furthermore, in the case of the engine oil composition of the present

invention, it is preferred that the coefficient of friction (reciprocating kinetic coefficient of friction) lies in the range not exceeding 0.100. Moreover, the hot tube test grading (engine cleaning property test; at 280°C) is preferably at least 5, more preferably at least 7 and still more preferably at least 8, and the hot tube test grading (engine cleaning property test; at 295°C) is preferably at least 2, more preferably at least 3.0 and still more preferably at least 3.5. The percentage change in the kinematic viscosity at 100°C in the

oxidation stability testing (ISOT) is preferably less than 0.5% and more preferably less than 0.25%.

Furthermore, the change in acid value in the oxidation stability testing (ISOT) is preferably less than

0.3 mgKOH/g, more preferably less than 0.2 mgKOH/g and still more preferably less than 0.15 mgKOH/g. Examples

Base oil

The base oils employed in the working examples and comparative examples have the properties shown in Table 1. Here, the kinematic viscosity (at 40°C) and the kinematic viscosity (at 100°C) are the values obtained based on JIS K2283 (Test Methods for Kinematic Viscosity and Method of Calculating the Viscosity Index of Crude Oil and

Petroleum Products) . Furthermore, the viscosity index is the value obtained based on JIS K2283 (Test Methods for Kinematic Viscosity and Method of Calculating the

Viscosity Index of Crude Oil and Petroleum Products) .

The pour point (P.P) is based on JIS K2269, the sulphur content is based on JIS K2541 (radiation excitation method), and the nitrogen content is based on JIS K2609 (chemical light emission method) .

Table 1

Glycerin- 1-oleate

The properties of the glycerin 1-oleate (glyceryl monooleate, GMO) employed in the working examples and comparative examples are as shown below. Here, the flash point is the value determined by the Cleveland open cup (COC) method in accordance with JIS K2265. Furthermore, the hydroxyl value is the value measured by means of the pyridine-acetyl chloride method based on JIS K0070.

melting point: 41°C

kinematic viscosity at lOODC: 11 mm ² /s

flash point (COC) : 220°C

hydroxyl value: 222 mgKOH/g

Amine ethylene oxide adduct

The properties of the amine ethylene oxide adduct

(DEA) employed in the working examples and comparative examples were as follows. Here, the base value is the value measured by means of the method in JIS K2501

(perchloric acid method) .

R = oleyl group [CH ₃ (CH ₂ ) ₇ -CH=CH- (CH ₂ ) _Ί - ]

n = 1

m = 1

melting point: 31°C

density: 0.92 g/cm ³

kinematic viscosity at 40°C: 69 mm ² /s

flash point (COC) : 230°C

hydroxyl value: 322 mgKOH/g

base value: 160 mgKOH/g

DI Additive Package

The main components of the DI additive package

(corresponding to GF-5) employed in the working examples and comparative examples were as follows {the component content in each case was calculated with the engine oil in the example taken as 100 m.cL S S "6 (9.05 m.cL S S "6 of said additive was added in the examples) } :

metal-based cleaning agent: Ca salicylate (Ca component = 0.21 m.cLsS"o # base value (HC1 method) =

6.7 mgKOH/g)

ashless dispersant: polybutenyl succinimide (N component = 0.095 m.cLsS"o # B component = 0.006 mass~6 )

zinc dialkyl dithiophosphate (secondary alkyl type, Zn component = 0.085 massl, P component = 0.074 mass%) metal deactivator

antioxidants: aromatic amine compound, hindered phenol compound

(Viscosity Index Improver)

The dispersant-viscosity index (VI) improver used is a polymethacrylate copolymer obtained from RohMax, with the commercial product name "Viscoplex 6-6955".

(Defoamer)

This was a 3 m.cL S S "6 solution of polydimethylsiloxane diluted with kerosene as solvent.

Evaluation Methods

Reciprocating Sliding Test Conditions

In order to determine the frictional characteristics, evaluation was carried out using a Cameron-Plint TE77 tester, based on ASTM-G-133 (American Society for Testing and Materials) . The upper test piece was circular- cylinder shaped, of diameter 6 mm, length 16 mm and made of SK-3, while the lower test piece was a sheet made of SK-3, and the testing was conducted for ten minutes at a test temperature of 80DC, load 300 N, amplitude 15 mm and reciprocating frequency 10 Hz, with the average value of the coefficient of friction measured over the stable final 1 minute period being recorded. The smaller the coefficient of friction, the more outstanding is the friction lowering property.

Hot tube testing

This was conducted by the Japan Petroleum Institute method, based on JPI-5S-55-99. Testing was carried out at two test temperatures, namely 280°C and 295°C. As an evaluation test of the high temperature deposit

prevention property in Japanese diesel engine oil standard JASO M355: 2008, a test temperature of 280°C is used, and a grading of 7.0 or above is taken as the Japanese diesel engine oil standard. The higher the grading, the better is the high temperature deposition prevention property.

Oxidation stability testing (ISOT)

Testing was carried out based on JIS-K-2514 at a test temperature of 165.5°C for a test time of 96 hours, and the items measured for evaluation were the increase (%) in the 100°C kinematic viscosity after testing and the level of change in acid value (mgKOH/g), with the results obtained being shown in Table 3.

Working Examples 1 to 4 and Comparative Examples 1 to 5

The compositions of the engine oils relating to Working Examples 1 to 4 and Comparative Examples 1 to 5 are shown in Table 2 (all figures in Table 2 are in ma s s i ) . The properties of said engine oils relating to Working Examples 1 to 4 and Comparative Examples 1 to 5 are shown in Table 3. The acid value is the value measured in accordance with JIS K2501. Table 2

Table 3

viscosity = % change in viscosity at 100°C; acid value = change in acid value, mgKOH/g

Table 4 shows the results of the evaluation of the friction reducing property for the engine oils relating to the working examples and comparative examples. As will be clear from this table, the coefficient of

friction is lowered by increasing the GMO, and a fuel saving effect is confirmed. On the other hand, with just the DEA, there is no fuel saving due to a coefficient of viscosity lowering effect. However, when the GMO and DEA are used in combination, a good coefficient of viscosity lowering effect is obtained. It is thought that there is hydrogen bonding between the nitrogen atom of the DEA and the hydrogen atoms of the GMO hydroxyl groups, with a strong dense adsorbed film due to the DEA and GMO being formed at the surface, so that the coefficient of

friction is further lowered.

Table 4: (Evaluation of the Viscosity Reducing Property; Coefficient of Viscosity in Cameron-Plint Reciprocating Kinematic Viscosity Testing)

Piston Cleaning Evaluation

Table 5 shows the results of the evaluation of the piston cleaning property for the engine oils relating to the working examples and comparative examples. As will be clear from this table, by using GMO and DEA in

combination, no great difference in the piston cleaning property was noted in the hot tube test at 280°C.

However, at the more severe high temperature of 295°C, the cleaning property was impaired throughout, and the cleaning grading lowered. In particular, the GMO has a double bond in the oleyl group region, so it tends to oxidize and degrade at high temperature. When the amount of added GMO is raised, the cleaning property is clearly lowered. However, when DEA is employed in combination therewith, there is a dramatic improvement in the

cleaning property. This is thought to be because the detergent action of the DEA, which is a surface active agent, is not impaired at high temperature, so an

additive effect can be seen.

Table 5 : Piston Cleaning Property Evaluation (Hot Tube

Testing Results)

test temperature: 280°C

Evaluation of Heat/Oxidation Stability

Table 6 and Table 7 show the results of the piston cleaning property evaluations in the case of the engine oils relating to the working examples and comparative examples. First of all, as will be clear from Table 6, in the case of just the GMO it can be seen that the percentage change in viscosity at 100°C following ISOT testing increases in proportion to the amount added, and it is apparent that adverse effects arise due to thermal and oxidative degradation of the test oil. This is thought to be because oxidative degradation of the double bond region of the oleyl group readily occurs at high temperature, as described above. However, when 0.5 wt% of DEA is added to the sample oil containing GMO, there is a dramatic lowering in the oxidative degradation, and the increase in viscosity is suppressed or improved. On the other hand, in the case of DEA by itself, as the added amount thereof is increased there is a tendency for the viscosity to rise but the extent is very low. It is only when the GMO and DEA are used in combination that the increase in viscosity brought about by thermal and oxidative degradation in this test is controlled, and kept low. It is concluded that there is a combination effect (a synergistic effect) operating between the GMO and DEA. The reason for this synergistic effect is not clearly understood, but it is thought that the DEA deactivates the surface of the Cu and/or Fe catalyst metals employed in the ISOT test, and so suppresses oxidative degradation.

Table 6 {Evaluation of Heat/Oxidation Stability (% Change in Viscosity in terms of the Kinematic Viscosity of Fresh Oil at 100°C) }

ISOT: 165.5°C 96 hours

Furthermore, Table 7 shows the results for the change in acid value of the degraded oil measured after ISOT testing. It will be clear from Table 7 that, as the amount of added GMO is increased, the acid value rises and so an acidic material is produced. Again, when the added amount of DEA is increased, there is also a slight tendency for the acid value to increase. However, when the GMO and DEA are employed in combination, there is practically no increase in acid value. The presence of a combination effect is clear from this.

Table 7 (Evaluation of Heat/Oxidation Stability)

165.5°C x 96 hours

in acid value compared to fresh oil, mgKOH/g

Added Amount of GMO

0.0 mass% 0.5 mass% 1 mass%

Added

0.0 mass% 0.1 0.5 0.8

Amount of

0.5 mass% 0.2 0.1 0.1

DEA

1.0 mass% 0.9 0.1 0.1