JP2003523456A - Lubricating oil composition - Google Patents

Abstract

(57) The present invention relates to a base stock and a compound of the general formula (I): Mo ₃ S _x- (Q), wherein x is 4 to 10, Q is a core group, A lubricating oil composition comprising an oil-soluble trinuclear organomolybdenum compound having at least one compound selected from the group consisting of a phenolic compound and an amine compound. is at least 85% kinematic viscosity (KV ₁₀₀₎ is about ^{2 × 10 -6 m 2 / sec~20} × 10 -6 m 2 / sec (2 cSt~20 cSt) and saturate content at 100 ° C. basestock And the composition. The composition has high oxidative stability, reduced deposit formation, and can provide good fuel economy improvements.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD OF THE INVENTION

The present invention relates to lubricating oil compositions rich in saturated hydrocarbons that resist oxidation, especially lubricants used in internal combustion engines.

BACKGROUND OF THE INVENTION

The lubricating oil composition is used for smooth operation of internal combustion engines, power transmission parts including automatic transmissions, shock absorbers, power steering devices and gears. The engine oil of an internal combustion engine, in particular, (i) lubricates the various sliding interfaces, such as between the piston ring and the cylinder liner, in the bearings of the crankshaft and connecting rod, and in the valve drive mechanism, including cams and valve lifters. ii) Cool the engine, (i
ii) functions to cleanly disperse combustion products and (iv) prevent corrosion and prevent rust.
The recent urgent demand for high performance engines means that the demands from the lubricants used in such engines have increased. Lubricating oils used in such engines typically contain oxygen and nitrogen oxides produced during the combustion of fuel and lubricants.
It deteriorates due to oxidation by (NOx) and that contained in blow-by gas caused by leakage of combustion gas to the crankcase through the piston-cylinder interface. The higher the engine performance requirements, the higher the NOx concentration in the blow-by gas. The detrimental effects of oxidation can be and have been mitigated by the use of various additives including antioxidants, antiwear additives, ashless detergents, friction modifiers and the like.

To date, this has been mitigated to some extent by the use of lubricating compositions containing Group I base oils that have relatively low saturated hydrocarbons (hereinafter “saturates”) despite their relatively high oxidation tendency. It was This means that the base oil itself is relatively inexpensive, but it had to be supplemented with a relatively large amount of additive / antioxidant to obtain the desired performance. However, by using relatively purified feedstocks such as highly saturated Group II and III basestocks, it is possible to obtain the desired performance without overly supplementing the additives / antioxidants. Is.

[0003]

[Details of the invention]

Here, it has been found that it is possible to use Group II or Group III basestocks with high performance in terms of oxidation stability and fuel efficiency by using a specific combination of antioxidants. It was Accordingly, the present invention provides a basestock and the following general formula: Mo ₃ S _x- (Q) (I) where x is 4 to 10, preferably 7, Q is a core group and a ligand. A lubricating oil composition containing an antioxidant containing an oil-soluble trinuclear organomolybdenum compound having a) and at least one other compound selected from a phenol compound and an amine compound, Kinematic viscosity (KV ₁₀₀ ) of basestock at 100 ℃ is about 2 × 1
0 ^-6 m ² / sec to 20 × 10 ^-6 m ² / sec (2 cSt to 20 cSt) and saturates content of at least 85%
The above composition.

The lubricating oil composition of the present invention has a KV ₁₀₀ of 2 × 10 ^{−6 to} 20 × 10 ⁻⁶ m ² / sec (2 to 20 cSt),
Preferably 2 × 10 ^-6 ~ 20 × 10 ^-6 m ² / sec (2 ~ 12 cSt) and saturates content of at least
A composition comprising a major amount of a Group II or Group III base stock which may be a natural or synthetic lubricating oil, which is 85%, preferably at least 88%. Specific examples of highly saturated Group II basestocks include, among others, RLOP 500R or Mobil Jurong 500N (
Saturates> 97%) or MXT 5 (saturates 92%); examples of Group III basestocks are in particular Yubase 4 (saturates content 99.5%) or Yubase 6 (saturates content). Is 97.5%). According to an embodiment, the invention further provides that the kinematic viscosity at 100 ° C. (KV ₁₀₀ ) is about 2 × 1.
0 ^-6 m ² / sec to 20 × 10 ^-6 m ² / sec (2 cSt to 20 cSt) and saturates content of at least 85%
A method of stabilizing a lubricating oil composition containing a base stock against oxidative degradation, wherein the base stock has the following general formula: Mo ₃ S _x- (Q) (I) (wherein x Is 4 to 10, preferably 7, Q is a core group, and may be a ligand.) And an oil-soluble trinuclear organomolybdenum compound having at least one other selected from phenol compounds and amine compounds. The method, comprising the step of adding an effective amount of an antioxidant comprising the compound.

The trinuclear molybdenum compound has the following formula (I) Mo ₃ S _x- (Q) (I) (wherein x is 4 to 10, preferably 7, and Q is a core group). . These compounds are relatively new and have been described in our previous U.S. patent application Ser.
No. 6,968. The disclosure of this prior U.S. patent regarding the structure, process and properties of the trinuclear molybdenum compounds is hereby incorporated by reference. In these compounds, the core group (Q) is a ligand capable of rendering the organomolybdenum compound of formula (I) oil-soluble and ensuring that the charge of said molybdenum compound is substantially neutral. Good. The core group (Q) is generally L _y (where L is a ligand and y renders the compound of formula (I) oil-soluble and neutralizes the charge of the compound of formula (I) as a whole. Have a sufficient number, type and charge to Therefore, more specifically, the trinuclear molybdenum compound used in the composition of the present invention may be represented by the formula (II): Mo ₃ S _x L _y (II).

The ligand “L” is suitably a dihydrocarbyl dithiocarbamate of the structure (—S ₂ CNR ₂ ), where the dihydrocarbyl group, R ₂ imparts oil solubility to the molybdenum compound. In this case, the term "hydrocarbyl" refers to a substituent having a carbon atom directly attached to the rest of the ligand, and is primarily hydrocarbyl of a nature within the scope of this invention. Such substituents include the following substituents. (1
) Hydrocarbon substituents, i.e. aliphatic substituents (e.g. alkyl or alkenyl),
Alicyclic substituents (eg cycloalkyl or cycloalkenyl), aromatic substitution,
Aliphatic-substituted, alicyclic-substituted aromatic rings, etc., or cyclic substituents in which the ring is completed via another ligand moiety (ie, the two indicated substituents can together form an alicyclic group) (2) Substituted hydrocarbon substituents, ie, substituents containing non-hydrocarbon groups that do not alter the properties of the predominant hydrocarbyls with which the invention is concerned. Those skilled in the art will appreciate that suitable groups (e.g., halo (especially chloro), amino, alkoxyl, mercapto, alkylmercapto, nitro, nitroso, sulfoxy, etc.); and (3) heterosubstituents, i. Substituents which are hydrocarbons of the nature of, but which contain atoms other than carbon present in the chain or ring composed of carbon atoms.

The hydrocarbyl group is preferably an alkyl group (eg, the carbon atom attached to the rest of the ligand “L” is a primary, secondary or tertiary carbon atom), an aryl group, a substituted aryl group and / or It is an ether group. Importantly, the hydrocarbyl group of the ligand must have a sufficient number of carbon atoms to make compound (I) soluble or dispersible in the oil to which the trinuclear organomolybdenum compound containing the ligand is added. I won't. The total number of carbon atoms present in all of the hydrocarbyl groups of the ligand of the organomolybdenum compound is suitably at least 21, preferably at least 25, more preferably at least 30, even more preferably at least 35, typically, for example: 21-800. For example, the number of carbon atoms in each hydrocarbyl group is generally in the range 1-100, preferably 1-40, more preferably 3-20. The antioxidant in the composition of the present invention also suitably comprises at least one other compound selected from phenolic compounds and amine compounds. A hindered phenol is preferable as the phenol compound.

Examples of such phenolic compounds include, in particular: Four,
4'-methylenebis (2,6-di-tert-butylphenol) 4,4'-bis (2,6-di-tert-butylphenol) 4,4'-bis (2-methyl-6-tert-butylphenol) 2 2,2'-methylenebis (4-ethyl-6-tert-butylphenol) 2,2'-methylenebis (4-methyl-6-tert-butylphenol) 4,4'-butylidenebis (3-methyl-6-tert-butylphenol) 4,4'-Isopropylidene bis (2,6-di-tert-butylphenol) 2,2'-Methylenebis (4-methyl-6-nonylphenol) 2,2'-Isobutylidene bis (4,6-Dimethylphenol ) 2,2'-Methylenebis (4-methyl-6-cyclohexylphenol) 2,6-di-tert-butyl-4-methylphenol 2,6-di-tert-butyl-4-ethylphenol and 2,4- Dimethyl-6-tert-butylphenol Individual hindered phenol preferable as an antioxidant is represented by the following general formula (III)
-(IV) (in the formula, R ₁ , R ₂ and R ₃ are alkyl groups having the same or different 3 to 9 carbon atoms, and x and y are integers of 1 to 4). You can

[0009]

[Chemical 2]

[0010]

[Chemical 3]

Suitable amine compounds for use in the compositions of the present invention are diarylamines, arylnaphthylamines, alkyl derivatives of diarylamines or alkyl derivatives of arylnaphthylamines. Preferred amine antioxidants are of formula (VII) or (VI
II) (wherein R ₄ and R ₅ are each a hydrogen atom, an alkyl group having 1 to 8 carbon atoms which are the same or different).

[0012]

[Chemical 4]

Specific examples of amine compounds that can be used in the composition of the invention include, in particular: monoalkyldiphenylamines such as monooctyldiphenylamine or monononyldiphenylamine; dialkyldiphenylamines such as 4,4′-dibutyldiphenylamine , 4,4'-dipentyldiphenylamine, 4,4'-dihexyldiphenylamine, 4,4'-diheptyldiphenylamine, 4,4'-dioctyldiphenylamine or 4,4'-dinonyldiphenylamine; polyalkyldiphenylamines such as tetra Butyldiphenylamine, tetrahexyldiphenylamine,
Tetraoctyldiphenylamine or tetranonyldiphenylamine; naphthylamine, for example α-naphthylamine or hexyl-α-naphthylamine; butylphenyl-α-naphthylamine, pentylphenyl-α-naphthylamine, hexylphenyl-α-naphthylamine, heptylphenyl-α-naphthylamine, Octylphenyl-α-naphthylamine or nonylphenyl-α-naphthylamine. Of these, dialkyldiphenylamine or naphthylamine is preferable.

In general, antioxidants containing organomolybdenum compounds with phenolic compounds and / or amine compounds are minor components of all lubricating oil compositions. For example, the organomolybdenum compound typically comprises from about 0.05 to about 5.00 wt% of the total composition, preferably 0.05 to 2.0 wt%, more preferably 0.1 to 0.7 wt%. That is, the molybdenum metal is suitably present in an amount of about 25 to 2500 ppm, preferably about 50 to 1000 ppm, more preferably 100 to 700 ppm and the phenolic compound and / or amine compound is
It is present in an amount of about 0.10 to about 3.0 wt% of the total composition. Further, when the weight ratio of the organic molybdenum compound to the phenol compound and / or the amine compound in the antioxidant is within the range of about 80:20 to about 20:80, these combined antioxidants of the present invention are used. Optimal retention of dispersibility can be achieved by. The antioxidant is, in addition to the organic molybdenum compound, a mixture of the above phenols (III) to (VI) and diarylamines (VII) to (VIII) at about 80:10:10 to about 10:30:60, respectively.
It is particularly preferred to include each preferably in a weight ratio typically in the range of 50:15:35.

The antioxidant may be mixed with the liquid carrier in the form of a concentrate. The concentration of the mixed antioxidant in the concentrate can be varied from 1 to 80% by weight, preferably in the range of 5 to 50% by weight. The antioxidants of the present invention can be used with any of the conventional dispersants previously used in lubricating oil compositions. Examples of such dispersants include, among others, polyalkylene succinimides, Mannich condensation products of polyalkylphenol-formaldehyde polyamines or borated derivatives thereof. However, it is preferred to use ashless dispersants, such as ashless succinimides, in particular polyamines, for example polyisobutenyl succinimide of tetraethylenepentamine or its homologues, benzylamine ashless dispersants or ester ashless dispersants. The dispersant is used in the composition of the present invention in an amount generally in the range of about 2 to 10% by weight, preferably about 4 to 8% by weight, based on the total weight of the lubricating oil composition.

A feature of the invention is that the trinuclear organomolybdenum compound of the composition of the invention facilitates control of deposit formation from engine oil. More specifically, for example, a product containing 200-750 ppm, preferably 450-550 ppm, of the Mo metal contribution from the trimer, 80-100 ppm of additional contribution from the detergent inhibitor package, was found to have deposit formation. Allows the amount to be significantly reduced. Adverse effects of the presence of the molybdenum compound in the product, for example
Any copper plate corrosion is easily mitigated by the inclusion of corrosion inhibitors or metal passivators in the product. This reduction in deposit formation was monitored by the so-called TEOST-MHT-2 test, which is similar to the commonly used TEOST-33 test method, but at relatively low temperatures for long periods of time. These tests are specifically designed to test GF-3 standard products. The TEOST-33 test is carried out with a temperature cycle varying from 200 to 500 ° C. and lasts for about 2 hours, resulting in a large oil oxidation (about 100 g). In contrast, TEOST-MHT-
The 2 test is a thin film test on hot engine deposits as measured in tests such as TU3HT, conducted at 285 ° C. for 24 hours and about 8 g of oil. TE
The OST-MHT-2 test measures deposits on heated rods or on the oil itself (filtered residue) and the GF-3 standard is considered to specify a deposit limit of 40 mg. From the results of the following examples, when the trinuclear organomolybdenum compound is present in the oil,
It can be seen that about 66% of the total weight of the produced deposit is reduced and meets the GF-3 standard.

Generally, these lubricating oil compositions comprise additives commonly used in lubricating oils, especially crankcase lubricants, such as antiwear additives, detergents, dispersants, rust inhibitors, Viscosity index improvers, extreme pressure agents, friction modifiers, corrosion inhibitors, emulsification aids, pour point depressants, defoamers and the like can be included. A feature of the present invention is that a lubricating oil composition containing a highly saturated base oil and a trinuclear organomolybdenum compound as an antioxidant with a phenolic compound and / or an amine compound unexpectedly improves oxidation control and significantly reduces fuel consumption. That is. In the case of lubricating oil compositions containing highly saturated base oils of diesel engine oils, viscosity control and dispersibility retention are better than compositions containing only one of these antioxidants used alone according to the invention. Added benefits. The present invention will be described more specifically with reference to the following examples.

[0018] Example General Procedure: it was prepared a series of test oil. These oils were then tested in a bench test conducted with 40 ppm iron from ferric acetylacetone ferric iron catalyzed at 165 ° C. under a nitrogen / air mixed flow. The flow rates of air and nitrogen are 500 ml / min and
It was controlled at 350 ml / min. The following commercially available materials were used in these tests. Irganox® L57 = Octylated / Butylated diphenylamine (eg Ciba Geigy) Irganox® L101 = High molecular weight phenolic antioxidant (eg Ciba Geigy) Irganox® L115 and Irganox® L 1035 = High molecular weight phenolic antioxidant having a thioether group (eg Ciba Geigy) Irganox® L06 = alkylated phenol-α-naphthylamine (eg Ciba Geigy) Irganox® L135 = high molecular weight phenolic antioxidant (eg , Ciba Geigy)

Irganox® L150 = a mixture of alkylated diphenylamines, phenolic antioxidants and phenolic antioxidants having thioether groups (eg Ciba Geigy) Paranox® 106 = polyisobutenylsuccinimide dispersants (eg ,
(Inphenium, Linden, NJ) Molyvan® 822 = Molybdenum dithiocarbamate molybdenum containing 5% wt. Molybdenum (eg RT Vanderbilt) PDN5203 = Trinuclear molybdenum dithiocarbamate containing 5% wt molybdenum Experimental Samples Paratone 8451 = Viscosity Index Enhancer (eg Oronite) Paraflow® 390 = Pour Point Depressant (eg Olonite) DI = Conventional Detergent Inhibitor Package Without Friction Modifier Package 120X = Saturate > 92% Group II base oil (eg Imperial Petroleum, Canada) where the same conventional DI package was used in all examples and tests.

Example AI Comparison of low saturates base oil and high saturates base oil: The composition of the test oils used in these examples and their respective viscosity changes after a 48 hour oxidation test are shown in Table 1 below.

[0021]

[Table 1] Table 1

[0022]

[Table 2] Table 1 continued ^* Contains 11.5% wt of molybdenum ^** Viscosity change after 48 hours oxidation test

From the above, while molybdenum trinuclear dithiocarbamate and diarylamine have individually good performance in low saturates base oils, unexpectedly, the combination of the two has individual components in high saturates base oils. It can be seen that it shows better performance.

Example JQ Comparison of Trinuclear Molybdenum Compound and Dinuclear Molybdenum Compound Table 2 below shows the composition of the test oils in Example JQ and the respective changes in the viscosity data after the 48-hour oxidation test.

[0025]

[Table 3] Table 2

[0026]

[Table 4] Table 2 continued ^* Change in viscosity after 48-hour oxidation test

From Example JQ it can be seen that the trinuclear molybdenum dithiocarbamate performs better in controlling oxidation than the conventional dinuclear molybdenum dithiocarbamate. The performance of the trinuclear molybdenum compound is further enhanced in highly saturated base oils.

Shows the change in viscosity after 32 hours oxidation test in Example RU Example RU in the following Table 3: [0028] synergy with the presence trinuclear molybdenum dithiocarbamates antioxidant mixture high saturates base oil.

[0029]

[Table 5] Table 3 ^* Contains 11.5% wt of molybdenum ^** Viscosity change after 48 hours oxidation test

Example RU demonstrates that a mixture of amine and phenolic antioxidants exhibits equivalent performance to amine antioxidants. Highly saturated base oils are also beneficial for viscosity control

Improved Fuel Economy : Fuel economy is measured in different types of engine tests including Sequence VIA, Sequence VIB and M111 tests. The Sequence VIA test and M111 test evaluate the initial fuel consumption, and the Sequence VIB test measures the initial consumption and fuel consumption after 96 hours. In all engine tests, fuel economy is measured as a function of lubricant fluid and boundary contributions to fuel economy. Lubricant contribution under fluid conditions is usually determined by a lubricant viscometer under low and high shear conditions, and lubricant contribution under boundary conditions is usually determined by friction modifying techniques. To illustrate the present invention, we concentrate on the lubricant contribution to the boundary working range of the engine, in the sequence VIB test, measured at stage 5 and sequence VIA at stage 1. Therefore, the following example is suitable for Stage 1
It shows the test performance in the test, the stage 5 test, and the M111 test.

Example V: A 5W-20 product containing a Group II base oil is shown in Table 4 below.

[0033]

[Table 6] Table 4 ^* Paratone® 8452 is sold by Oronite, Richmond, California, USA. ^** Parabar®, Paranox® and SAP additives are sold by Inphenium, Linden, NJ, USA.

Fuel consumption and fuel consumption retention data are based on the M111 fuel consumption test (CES-L54-X-94) and M1 for gasoline passenger cars.
Collected using 11 fuel economy retention tests. In the M111 fuel consumption retention test, the standard test cycle is repeated 21 times to extend the test time. Each test cycle is followed by a steady state aging period. Aging is equivalent to about 805 km (500 miles). Therefore, the entire test corresponds to about 16093 km (about 10,000 miles) and takes about 185 hours. Fuel consumption is measured every cycle, that is, about every 805 km (500 miles). The fuel economy standard RL191 is measured at the beginning and end of the test, thus allowing continuous aging of the test oil. Table 5 below shows the effect of molybdenum trinuclear dithiocarbamate on fuel economy and fuel economy retention. Therefore, the improved data for initial combustion consumption is based on comparison with the industrial standard oil RL191 (which is a 15W-40 engine oil).

[0035]

[Table 7] Table 5 ^* Sakaralube (registered trademark) 155 is a dinuclear dithiocarbamate Mo (5% wt Mo, for example,
Asahi Denka KK).

From Example V it can be seen that the addition of molybdenum compounds results in better fuel economy retention in European gasoline passenger car engines. The use of trinuclear molybdenum dithiocarbamate significantly improves the initial fuel economy and fuel economy retention as compared to the conventional molybdenum dinuclear dithiocarbamate.

Example W: A 5W-20 engine oil product containing a Group III base oil is shown in Table 6 below.

[0038]

[Table 8] Table 6 ^* Paratone® 8464 is sold by Oronite, Richmond, California, USA.

Sequence VIA screen data for Stages 1, 4 and 7 (stages sensitive to friction modifiers) using trinuclear molybdenum dithiocarbamate are shown in Table 7. The% improvement in fuel economy was measured against Sequence VIA's industrial baseline test oil (BC-3) (BC-3 is a non-friction adjusted synthetic 5W-30).

[0040]

[Table 9] Table 7

Thus, Example W further demonstrates the benefits of trinuclear molybdenum dithiocarbamate in improving fuel economy of North American gasoline engines.

Example X: TEOST-in a manner very similar to the conventional TEOST-33 test of the GF-2 standard by running at low temperature (285 ° C.) for a long time, ie 24 hours, on a sample of 8 g of oil. MHT-2 test was performed. A test was set up to measure deposits formed on the heated rod or oil itself (filtered residue) and was expected to meet the currently indicated GF-3 standard 40 mg deposit limits. The results are shown in Table 8 below.

[0043]

[Table 10] Table 8

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) C10M 159/18 C10M 159/18 // C10N 10:12 C10N 10:12 20:02 20:02 30:10 30:10 40:25 40:25 (72) Torkelson Jeffrey Robert New Jersey, USA 08801 Mont Laurel (no street number) (72) Inventor Woolley Paul Es England Berkshire Earlsey 14 7 XB Newbury Equine Way 33 F-term (Reference) 4H104 BA07A BB05C BE07C BG10C DA02A DA03A DB04C EA02 EB02 FA06 LA05 PA41

Claims (12)

[Claims] 1. A base stock and the following general formula: Mo ₃ S _x- (Q) (I) (wherein x is 4 to 10, preferably 7, Q is a core group and a ligand And an oil-soluble trinuclear organomolybdenum compound having the formula (1) and at least one other compound selected from a phenol compound and an amine compound. The kinematic viscosity (KV ₁₀₀ ) of base stock at 100 ℃ is about 2
× 10 ^-6 m ² / sec to 20 × 10 ^-6 m ² / sec (2 cSt to 20 cSt) and saturate content of at least
85%, said composition being characterized. 2. The base stock is a Group II or Group III base stock, K
The composition according to claim 1, which may be a natural or synthetic lubricating oil having a V ₁₀₀ of 2 × 10 ^{−6 to} 12 × 10 ⁻⁶ m ² / sec (2 to 12 cSt). 3. The trinuclear molybdenum compound has the following formula (I) Mo ₃ S _x- (Q) (I), wherein x is 7 and Q is a core group. Or the composition according to 2. 4. A ligand capable of ensuring that the core group Q makes the organomolybdenum compound of formula (I) oil soluble and that the charge of the molybdenum compound is substantially neutral. The composition according to any one of claims 1 to 3, which is: 5. The phenolic compound is a hindered phenol.
The composition according to any one of 1 to 4. 6. The amine compound is represented by the following formula (VII) or (VIII) (wherein R ₄ and R ₅
Are each a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, which may be the same or different.
The composition according to any one of claims 1 to 5, which is selected from one or more of a diarylamine having a), an arylnaphthylamine, an alkyl derivative of a diarylamine, and an alkyl derivative of an arylnaphthylamine. [Chemical 1] 7. The antioxidant comprising the trinuclear organomolybdenum compound and at least one other compound selected from phenol compounds and / or amine compounds constitutes a minor component of the total lubricating oil composition. 7. The composition according to any one of claims 1-6. 8. The method according to claim 1, wherein the antioxidant containing the trinuclear organomolybdenum compound and an amine compound constitutes a minor component of the total lubricating oil composition.
The composition according to paragraph 1. 9. The trinuclear organomolybdenum compound is present in the composition in an amount of about 1% of the total composition.
9. The composition of any one of claims 1-8, present in an amount of 0.05 to about 5.00 wt%. 10. The composition of any one of claims 1-9, wherein the amount of phenolic and / or amine compounds present in the composition is from about 0.10 to about 3.0 wt% of the total composition. Composition. 11. A basestock having a kinematic viscosity (KV ₁₀₀ ) at 100 ° C. of about 2 × 10 ^{−6 to} 20 × 10 ⁻⁶ m ² / sec (2 cSt to 20 cSt) and a saturate content of at least 85%. A method of stabilizing a lubricating oil composition containing oxidative decomposition, wherein the basestock has the following general formula: Mo ₃ S _x- (Q) (I) (where x is from 4 to 10). , Preferably 7, Q is a core group, and may be a ligand.) And an oil-soluble trinuclear organomolybdenum compound having at least one other compound selected from a phenol compound and an amine compound. The method comprising the step of adding an effective amount of an antioxidant comprising: 12. The kinematic viscosity (KV ₁₀₀ ) at 100 ° C. is about 2 × 10 ⁻⁶ m ² / sec to 20 ×.
A method for improving the fuel economy of a lubricating oil composition comprising a base stock having a saturated content of at least 85% at 10 ^-6 m ² / sec (2 cSt to 20 cSt), wherein Oil-soluble trinucleus having the formula: Mo ₃ S _x- (Q) (I) (wherein x is 4 to 10, preferably 7, Q is a core group and may be a ligand.) The above method, comprising the step of adding an effective amount of an antioxidant containing an organic molybdenum compound and at least one other compound selected from a phenol compound and an amine compound.