EP0737735A2

EP0737735A2 - Lubricant oil composition with reduced friction coefficient

Info

Publication number: EP0737735A2
Application number: EP96302490A
Authority: EP
Inventors: Satoshi Asano; Katsuya Arai
Original assignee: Tonen Corp
Current assignee: Tonen General Sekiyu KK
Priority date: 1995-04-14
Filing date: 1996-04-09
Publication date: 1996-10-16
Also published as: SG54284A1; JPH08283762A; AU5062796A; EP0737735A3; CA2173895A1

Abstract

A lubricant oil composition produced by blending (A) a molybdenum-containing friction conditioner, (B) a boron-containing compound and (C) an antioxidant if necessary, with a lubricant base oil, wherein the content of the molybdenum derived from the molybdenum-containing friction conditioner is 100 to 2,000 ppm (as the ratio by weight) and the content of the boron derived from the boron-containing compound is 0.015% by weight or more, to the total weight of the composition. The lubricant oil compositions of the present invention are the lubricant oil compositions blended with a molybdenum-containing friction conditioner and a boron-containing compound, and are capable of decreasing coking deposit in internal combustion engines such as automobile engines, which is advantageous for sustaining a fuel-efficiency property for a long term. Hence, the compositions can be used preferably for automobile lubricant oils.

Description

The present invention relates to a novel lubricant oil composition. More specifically, the present invention relates to a lubricant oil composition with a small friction coefficient under a wide variety of applicable conditions, particularly under operating conditions at a medium to low oil temperature and a low-speed rotation, which is preferable as a lubricant oil composition for internal combustion engines such as automobile engines for sustaining a fuel-efficiency.
So as to smoothly operate internal combustion engines, driving systems such as automatic transmissions, buffers, and power steerings, and gears, use has been made therein of lubricant oils. Lubricant oils for internal combustion engines, in particular, have roles in lubricating principally a variety of sliding parts such as piston rings/cylinder liners, bearings of a crank shaft and connecting rods, valve mechanism inclusive of cams and valve lifters, and the like, as well as in cooling the inside of an engine and cleaning to disperse combustion products and furthermore preventing rust and corrosion.
As has been described above, a wide variety of efficiencies are demanded of lubricant oils for internal combustion engines. In recent years, furthermore, higher efficiency has been required therefor, as internal combustion engines have acquired higher performance and higher output and the operating conditions have become more severe. In order to satisfy such demanded properties, thus, a variety of additives including for example wear preventing agents, metal cleaning agents, non-ash dispersants, antioxidants and the like have been added to lubricant oils for internal combustion engines.
For the fundamental functions of lubricant oils for internal combustion engines, smooth operation of internal combustion engines under any of the conditions, in particular, is significant, so as to prevent wear and seizure. Lubricated engine parts are mostly in the state of fluid lubrication, but valve systems and top and bottom dead centers of pistons are likely to be put in the state of boundary lubrication. The wear preventing property in such a state of boundary lubrication is generally given by the addition of zinc dithiophosphate and zinc dithiocarbamate. The energy loss due to friction of moving parts involving lubricant oils is so large in internal combustion engines that use is made of a lubricant oil in combination with a variety of additives primarily including a friction conditioner, as a measure for decreasing a frictional loss or for increasing the fuel efficiency (for example, see Japanese Patent Publication No. 23595/1991).
Automobile internal combustion engines are operated at a wide range of oil temperature, and rates of rotation and load, and so as to promote the fuel-efficiency, lubricant oils for internal combustion engines should have greater friction properties under a wide variety of applicable conditions. However, the friction properties may be sometimes deteriorated by generated coking deposit and the like. Thus, so as to maintain the fuel-efficiency for a long term, less coking deposit should be demanded. Hence, the standard ILSAC GF-2 specifying such demand is now going to be established.
On the other hand, so as to lower the friction coefficient, use has been made of molybdenum-containing friction conditioners such as sulfoxymolybdenum dithiocarbamate. When the improvement of the fuel-efficiency is intended by decreasing the friction coefficient by means of the molybdenum-containing friction conditioner, the coking deposit is increased in proportion to the molybdenum content thereof, disadvantageously, involving sometimes the occurrence of such a drawback that the fuel-efficiency property which has been laboriously realized cannot be maintained.
Practically, some lubricant oil compositions blended with such molybdenum-containing friction conditioners have a drawback such that in a deposit test according to the hot tube coking test of the GF-2 standard, they absolutely cannot satisfy the standard [the deposit content at the hot tube coking (at 310°C for 16 hours) should be 100 mg or less] because occlusion develops in them through the coking deposit.
The objective of the present invention is to improve the property of sustaining the fuel-coefficiency of a lubricant oil composition with a smaller friction coefficient, the composition being blended with a molybdenum-containing friction conditioner, more specifically, to provide a lubricant oil composition blended with a molybdenum-containing friction conditioner, the composition satisfying the coke deposit criterion of the GF-2 standard on hot tube coking test.
It has been discovered that coke deposit can be decreased prominently by adding a specific amount of a specific compound having a higher boron content into a lubricant oil composition with friction properties improved by use of a molybdenum series additive.
More specifically, the present invention is to provide:

(1) a lubricant oil composition produced by blending (A) a molybdenum-containing friction conditioner and (B) a boron-containing compound with a lubricant base oil, wherein the content of the molybdenum derived from the molybdenum-containing friction conditioner is 100 to 2,000 ppm (as the ratio by weight) and the content of the boron derived from the boron-containing compound is 0.015% by weight or more, to the total weight of the composition; and
(2) a lubricant oil composition produced by blending (A) a molybenum-containing friction conditioner, (B) a boron-containing compound and (C) a minor amount of an antioxidant with a lubricant base oil, wherein the content of the molybdenum derived from the molybdenum-containing friction conditioner is 100 to 2,000 ppm (as the ratio by weight) and the content of the boron derived from the boron-containing compound is 0.015% by weight or more, to the total weight of the composition.

Furthermore, preferable embodiments of the present invention include:

(3) a lubricant oil composition according to 1 or 2 above, wherein the molybdenum-containing friction conditioner is sulfoxymolybdenum dithiocarbamate;
(4) a lubricant oil composition according to 1, 2 and 3 above, wherein the boron-containing compound is boron-containing succinimide or boron-containing succinate ester;
(5) a lubricant oil composition according to 2 to 4 above, wherein the content of the antioxidant is 0.05 to 5.0% by weight, to the total weight of the composition; and
(6) a lubricant oil composition according to 2 to 5 above, wherein the anti-oxidant is phenol sulfide.

The present invention is described hereafter with reference to the accompanying drawings in which:

Figure 1 is a graph representing the relation between the molybdenum content and the amount of deposit generated; and
Figure 2 is a graph representing the relation between the boron content and the amount of deposit generated.

In the lubricant oil compositions in accordance with the present invention, any lubricant base oil may be used with no specific limitation; use may be made of those base oils conventionally used as the base oils of lubricant oils, for example, mineral oils and synthetic oils. Mineral oils include, for example, raffinate produced through the solvent refining of lubricant oil raw materials in aromatic extraction solvents such as phenol,N-methylpyrolidone and furfural; hydrogenated oils produced by hydrogenation using a hydrogenation catalyst such as cobalt and molybdenum on a carrier silica-alumina; or mineral oils such as lubricant fractions produced by isomerization of wax, for example, 60 Neutral Oil, 100 Neutral Oil, 150 Neutral Oil, 300 Neutral Oil, 500 Neutral Oil, bright stock and the like. Alternatively, synthetic oils include poly(α-olefin oligomer), polybutene, alkylbenzene, polyol ester, polyglycol ester, dibasic acid ester, phosphate ester, silicone oil and the like may be used. These base oils may be used singly or in combination with two or more thereof. Likewise, mixtures of such mineral oil and such synthetic oil may be used. Preferably the base oil has a kinematic viscosity generally in a range of 3 to 20 mm²/s at a temperature of 100°C.
As the molybdenum-containing friction conditioner to be used for the friction conditioner of the present invention, any molybdenum-containing compound may be used with no specific limitation, provided that the compound has an action of decreasing the friction property when added to a lubricant oil. For example, use may be made of sulfoxymolybdenum dithiocarbamate, sulfoxymolybdenum dithiophosphate, molybdenum oxide ester and molybdenum amine salt and the like, and the derivatives thereof, having an alkyl substititent with 1 to 18 carbon atoms.
As the molybdenum-containing friction conditioner in accordance with the present invention, use may be made of one or two or more of these molybdenum compounds preferably.
In accordance with the present invention, the molybdenum-containing friction conditioner may be blended within a range of having the effect of decreasing a friction coefficient, that is, at such an amount that the content of the molybdenum derived from the molybdenum-containing friction conditioner should be 100 to 2,000 ppm (as the ratio by weight), preferably 200 to 2,000 ppm (as the ratio by weight), more preferably 400 to 1,500 ppm (as the ratio by weight) and most preferably 600 to 1,300 ppm (as the ratio by weight) to the total weight of the lubricant oil composition. When the molybdenum-containing friction conditioner is blended at such an amount that the content of the molybdenum derived from the molybdenum-containing friction conditioner is below 100 ppm (as the ratio by weight) to the total weight of the composition, the effect of improving the friction property cannot be satisfactorily exerted. When the molybdenum-containing friction conditioner is blended at such an amount that the content of the molybdenum derived from the molybdenum-containing friction conditioner is above 2,000 ppm (as the ratio by weight) to the total weight of the composition, the improvement in the friction decreasing effect cannot be brought about in proportion to the amount; additionally, such an amount is likely to cause the generation of coking deposit.
When only the molybdenum-containing friction conditioner is added into a lubricant oil, the lubricant oil rapidly falls into an occlusive state supposing the molybdenum content is above 100 ppm at the hot coking test as shown in Figure 1.
As the sulfoxymolybdenum dithiocarbamate to be used preferably in the lubricant oil composition of the present invention with respect to the effect of decreasing friction, preferably, use may be made of a compound represented by the general formula [1]:
wherein R¹ and R² are hydrocarbon groups with 8 to 18 carbon atoms, respectively, and they may be the same or different from each other; "m" and "n" are individually positive integers in which the sum thereof is 4.
The hydrocarbon groups with 8 to 18 carbon atoms, represented by R¹ and R² in the general formula [1], include for example hydrocarbon groups such as alkyl groups with 8 to 18 carbon atoms; alkenyl groups, with 8 to 18 carbon atoms; cycloalkyl groups with 8 to 18 carbon atoms; allyl groups, alkylallyl groups and allylalkyl groups with 8 to 18 carbon atoms. The alkyl groups and the alkenyl groups may be in the form of a straight chain or otherwise in the form of a branched chain. The hydrocarbon groups represented by R¹ and R² have particularly preferably eight carbon atoms in the lubricant oil composition of the present invention.
Specific examples of the hydrocarbon groups represented by R¹ and R² include octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, octenyl, nonenyl, decenyl, undecenyl, dodecenyl, tridecenyl, tetradecenyl, hexadecenyl, octadecenyl, dimethylcyclohexyl, ethylcyclohexyl, methylcyclohexylmethyl, cyclohexylethyl, propylcyclohexyl, butylcyclohexyl, hepthylcyclohexyl, dimethylphenyl, methylbenzyl, phenetyl, naphthyl, dimethylnaphthyl and the like.
For the lubricant oil composition of the present invention, one type of sulfoxymolybdenum dithiocarbamates may be used; otherwise, two types or more thereof may be used mixed with each other. Additionally, sulfoxymolybdenum dithiocarbamate may be blended at such an amount that the content of the molybdenum derived from sulfoxymolybdenum dithiocarbmate should be 100 to 2,000 ppm (as the ratio by weight), preferably 200 to 2,000 ppm (as the ratio by weight), more preferably 400 to 1,500 ppm (as the ratio by weight) and most preferably 600 to 1,300 ppm (as the ratio by weight), to the total weight of the composition. When sulfoxymolybdenum dithiocarbamate is blended at such an amount that the content of the molybdenum derived from sulfoxymolybdenum dithiocarbamate is below 100 ppm (as the ratio by weight) to the total weight of the composition, the effect of improving the friction property cannot satisfactorily be exerted; otherwise, when sulfoxymolybdenum dithiocarbamate is blended at such an amount that the content of the molybdenum derived from sulfoxymolybdenum dithiocarbamate is above 2,000 ppm (as the ratio by weight) to the total weight of the composition, the effect of decreasing the friction property cannot be improved in proportion to the content; furthermore, the generation of coking deposit might be likely to be caused.
The boron-containing compound containing a high percentage of boron, capable of suppressing coking deposit, by which the present invention is characterized, has conventionally been added as a dispersant, for example, at a trace amount below 0.015% by weight as the boron content, to a lubricant oil. However, so as to acquire the effect of preventing coking deposit in accordance with the present invention, the compound should necessarily be added above 0.015% by weight, calculated in terms of boron.
Embodying examples of the boron-containing compounds containing a high percentage of boron, capable of suppressing coking deposit, by which the present invention is characterized, include boron-containing succinimide, boron-containing succinate ester and the like. The boron-containing succinimide includes for example those represented by the following general formulas [2] and [3].

where R³ represents a hydrocarbon group with 1 to 50 carbon atoms, R⁴ represents an alkylene group with 2 to 5 carbon atoms, and "n" is an integer of 1 to 10; in the compound of the general formula [3], the two R³'s may be the same or different from each other; the R⁴'s of the number "n" in the general formula [2] and the R⁴'s of the number "n+1" in the general formula [3] may be the same or different from each other, respectively; Z represents a boron-containing substituent, including for example
More specifically, ECA 5025 (manufactured by Exxon Chemical Co., Ltd.), LUBRIZOL 935 (manufactured by Lubrizol Co., Ltd.) and the like may be viewed as illustrative.
Furthermore, boron-containing succiniate esters include for example those represented by the general formula [5].
wherein "n" represents an integer of 1 to 20; R⁵ represents a straight or branched hydrocarbon group with 2 to 18 carbon atoms, which may contain any aromatic groups or double bonds; Y and Z are boron-containing substituents, respectively, at least one of which is bound through a coordinate bond to the succinate ester).
Specifically, for example, LUBRIZOL 936 (manufactured by Lubrizol Co., Ltd.) may be viewed as illustrative.
In accordance with the present invention, the effect of adding boron-containing succinimide and/or boron-containing succinate ester is necessary, and furthermore the amount thereof to be added is extremely critical.
For example, when the boron content is above 0.015% by weight to a lubricant oil composition having a molybdneum content of 1,000 ppm (as the ratio by weight), the coking deposit decreases along the steep curve as shown in Figure 2. The deposit amount rapidly decreases below 100 mg from the occlusive state.
Therefore, as shown in the figure, no specific adverse effect will be brought about by the addition thereof above the critical value, but the effect of decreasing the coking deposit will never be increased in proportion to the amount thereof to be added.
In the lubricant oil composition of the present invention, the boron-containing compound should be blended at such an amount that the content of the boron derived from the boron-containing compound is above 0.015% by weight, preferably above 0.030% by weight, to the total weight of the composition.
When the boron-containing compound is blended at such an amount that the content of the boron derived from the boron-containing compound is below 0.015% by weight, the effect of preventing coking deposit is not satisfactorily exerted.
In the lubricant oil composition of the present invention, one type or a combination of two types or more of the boron-containing compounds may be used.
The amount of deposit has some relation with the molybdenum content and the boron content. As shown in the examples described below, the suppressive effect of deposit gets higher at a lower molybdenum content, provided that the boron content is fixed at a given value. Furthermore, the suppressive effect of deposit gets higher at a higher boron content, provided that the molybdenum content is fixed at a given value.
Within the limits not detrimental to the objective of the present invention, a wide variety of additives conventionally used in lubricant oils, may be added appropriately to the lubricant oil composition of the present invention, including for example antioxidants, metal cleaning agents, other friction conditioners, viscosity index improvers, pour point depressants, defoaming agents, other wear preventing agents, rust preventives, corrosion inhibitors and the like. Preferably, these additives have a structure not subject to dehydrogenation reaction, from the viewpoint of decreasing coking deposit.
Among these additives, the antioxidants in particular are preferable because the generation of coking deposit can be decreased by suppressing the progress of radical polymerization. The antioxidants which can be used in the present invention include for example amine-series antioxidants such as alkylated diphenylamine, phenyl-α-naphthylamine, alkylated α-naphthylamine, and phenol-series antioxidants such as 2,6-di-t-butyl-4-methylphenol, 4,4'-methylenebis(2,6-di-t-butylphenol), phenol sulfide, etc. These are used generally at a ratio of 0.05 to 5% by weight. Among these antioxidants, a phenol-series antioxidant with greater radical-capturing function is preferable in particular.
The metal-series cleaning agents include for example calcium sulfonate, magnesium sulfonate, barium sulfonate, calcium phenate, barium phenate, calcium salicylate, magnesium salicylate and the like, and these may be used generally at a ratio of 0.1 to 5% by weight.
The friction conditioners include for example polyhydric alcohol partial ester, amine, amide, sulfide ester and the like.
The viscosity index improvers include for example polymethacrylate-series, polyisobutylene-series, ethylene-propylene copolymer-series, styrene-butadiene hydrogenated copolymer series and the like, and these may be used generally at a ratio of 0.5 to 35% by weight.
The pour point depressants include for example polyalkylmethacrylate, chlorinated paraffin-naphthalene condensate and the like.
The defoaming agents include for example dimethylpolysiloxane, polyacrylic acid and the like.
The wear preventing agents include for example thiophosphate metal salt, thiocarbamate metal salt, sulfur compound, phosphate ester, phosphite ester and the like, and these may be used generally at a ratio of 0.05 to 5.0% by weight.
The rust preventives include for example fatty acid, alkenylsucciniate semi-ester, fatty acid soap, alkylsulfonate, fatty acid polyhydric alcohol ester, fatty acid amine, oxidized paraffin, alkylpolyoxyethylene ether and the like.
The corrosion inhibitors include for example benzotriazole, benzoimidazole and the like, thiadiazoles and the like.
The present invention will now be apparent from the following more particular description of the examples, but it will be understood that the examples do not purport to be wholly definitive with respect to the scope of the invention.
In the examples and comparative examples, herein, the hot tube cooling test was carried out and assessed by means of Hot Tube Coking Test (HTCT) manufactured by Komatsu Kabushiki Kaisha. HTCT was carried out as follows: after passing individual sample oils through a glass tube having a 2 mm inner diameter and a 300 mm length at air flow of 10 ± 0.5 cc/min., oil flow of 0.31 ± 0.01 cc/hour, a temperature of 310°C for 16 hours, the glass tube was washed in n-hexane and dried sufficiently to measure the weight of the coking deposit attached to the inside of the glass tube.

EXAMPLES 1 TO 7

A lubricant oil composition was prepared such that as a molybdenum-containing friction conditioner, 1,000 or 1,500 ppm of sulfoxy-molybdneum-N,N-dioctyl dithocarbamate, calculated in terms of molybdenum, and as a boron-containing compound, 0.015 to 0.140% by weight of borated succinimide (LUBRIZOL 935, manufactured by Lubrizol Co., Ltd.), calculated in terms of boron were contained, respectively, in a base oil (100 Neutral Oil with a viscosity of 4.4 mm²/s at 100°C). The deposit was measured by the hot tube coking test. The results are shown in Table 1.
The lubricant oil compositions containing 1,000 ppm molybdenum of Examples 1 to 5 in accordance with the present invention generated less HTCT coke deposit, which decreased as the increase in the boron content. Additionally, the lubricant oil compositions having an increased molybdenum content of 1,500 ppm of Examples 6 and 7 generated less HTCT coke deposit. However, when the compositions of Examples 3 and 6, both of which have the same boron content, are compared with each other and the compositions of Examples 5 and 7, both of which have the same boron content, are compared with each other, those of Examples 3 and 5, with a lower molybdenum content, generated less HTCT coke deposit, which indicates that those with a lower molybdenum content in such a range generate less HTCT coke deposit.

COMPARATIVE EXAMPLE 1

The same procedure was carried out as in Examples 1 to 5, except that the boron-containing succinimide to be blended was decreased to a content of 0.013% by weight, calculated in terms of boron. Then, the HTCT coke deposit was 211.8 mg in weight, which exceeded the GF-2 standard.

COMPARATIVE EXAMPLE 2

The same procedure was carried out as in Examples 1 to 5, except that succinimide was blended at 3.0% by weight, instead of the boron-containing succinimide. The resulting composition did not contain boron. Occlusion occurred at the hot tube coking test.

EXAMPLES 8 TO 13

The same procedure was carried out as in Examples 1 to 7, except that sulfoxymolybdenum-N,N-ditridecyl dithiocarbamate was used as the molybdenum-containing friction conditioner, which was blended at a content of 100 and 400 ppm, calculated in terms of molybdenum. The results are shown in Table 2.
The lubricant oil compositions of Examples 8 to 13 generated less HTCT coke deposit. The same results are yielded as those in Examples 1 to 7 to the effect that the increase in the boron content decreased HTCT deposit and a lower molybdenum content generated less HTCT deposit in such a range, provided that the boron content was fixed at a given value.

COMPARATIVE EXAMPLE 3

The same procedure was carried out as in Examples 8 and 9, except that boron-containing succinimide to be blended was decreased to a content of 0.013% by weight, calculated in terms of boron. The HTCT coke deposit was 132.9 mg in weight, which exceeded the GF-2 standard.

EXAMPLES 14 AND 15

The same procedure was carried out as in Examples 1 to 5, except that boron-containing succinate ester (LUBRIZOL 936, manufactured by Lubrizol Co., Ltd.) was used as the boron-containing compound, which was blended at a content of 0.015 or 0.030% by weight, calculated in terms of boron. The results are shown in Table 3.

EXAMPLES 16 AND 17

The same procedure was carried out as in Examples 8 and 9, except that boron-containing succinate ester (LUBRIZOL 936, manufactured by Lubrizol Co., Ltd.) was used as the boron-containing compound, which was blended at a content of 0.015 or 0.030% by weight, calculated in terms of boron. The results are shown in Table 4.
All the lubricant oil compositions of Examples 14 to 17 satisfy the GF-2 standard. However, boron-containing succinimide to be used as the boron-containing compound obtained slightly better results than boron-containing succiniate ester, provided that the boron content was at a given value.

EXAMPLES 18 TO 26

With respect to the lubricant oil compositions of Examples 1 to 5, to which was further added an antioxidant, an examination was made of their properties.
A lubricant oil composition was prepared such that as a molybdenum-containing friction conditioner, 1,000 ppm of sulfoxymolybdenum-N,N-dioctyl dithiocarbamate, calculated in terms of molybdenum, and as a boron-containing compound, 0.015 to 0.140% by weight of succinimide (LUBRIZOL 935, manufactured by Lubrizol Co., Ltd.) calculated in terms of boron, and as an antioxidant, 0.7 or 1.4% by weight of phenol sulfide were contained, respectively, in a base oil (100 Neutral Oil with a viscosity of 4.4 mm²/s at 100°C). The deposit was measured by the hot tube coking test. The results are shown in Table 5.
Comparing the results of Examples 18 to 22 with the results of Examples 1 to 5, it will be noted that the mixtures of the same amounts of the molybdenum-containing friction conditioner and the boron-containing compound generated less HTCT coke deposit through the addition of the antioxidant. Furthermore, comparing the results of Examples 18 to 22 with the results of the Examples 23 to 26, it will be noted that less HTCT coke was deposited in the case of the same amounts of the molybdenum-containing friction conditioner and the boron-containing compound, as the amount of the antioxidant to be added in such a range was increased. Based on these results, the effect of the antioxidant were able to be verified in the lubricant oil compositions in accordance with the present invention.

EXAMPLE 27

Further adding an antioxidant, that is, phenol sulfide at 0.7% by weight to the compound of Example 14, a lubricant oil composition was prepared. Then, the hot tube coking test was carried out. The HTCT coke deposit was 81.6 mg in weight. The results are shown in Table 6.

EXAMPLE 28

Further adding an antioxidant, that is, phenol sulfide at 0.7% by weight to the compound of Example 16, a lubricant oil composition was prepared. Then, the hot tube coking test was prepared. The HTCT coke deposit was 5.0 mg in weight. The results are shown in Table 7.
The lubricant oil compositions of Examples 27 and 28 generated less HTCT coke deposit than the deposit generated from those with no blend of the corresponding antioxidant. In Example 28, in particular, the effect of the antioxidant was prominent.

As is seen, the lubricant oil compositions of the present invention are the lubricant oil compositions blended with a molybdenum-containing friction conditioner and a boron-containing compound, and are capable of decreasing coking deposit in internal combustion engines such as automobile engines, which is advantageous for sustaining a fuel-efficiency property for a long term. Hence, the compositions can be used preferably for automobile lubricant oils.

TABLE 1

	Molybdenum (ppm)	Boron (wt%)	HTCT Deposit (mg)
Example 1	1,000	0.015	82.5
Example 2	1,000	0.030	17.8
Example 3	1,000	0.050	1.8
Example 4	1,000	0.080	1.6
Example 5	1,000	0.140	1.4
Example 6	1,500	0.050	13.7
Example 7	1,500	0.140	1.7
Comparative Example 1	1,000	0.013	211.8
Comparative Example 2	1,000	0.000	occluded

TABLE 2

	Molybdenum (ppm)	Boron (wt%)	HTCT Deposit (mg)
Example 8	100	0.015	52.4
Example 9	100	0.030	0.8
Example 10	400	0.015	68.3
Example 11	400	0.030	1.9
Example 12	400	0.050	1.0
Example 13	400	0.140	0.3
Comparative Example 3	100	0.013	132.9

TABLE 3

	Molybdenum (ppm)	Boron (wt%)	HTCT Deposit (mg)
Example 14	1,000	0.015	93.9
Example 15	1,000	0.030	38.5

TABLE 4

	Molybdenum (ppm)	Boron (wt%)	HTCT Deposit (mg)
Example 16	100	0.015	66.9
Example 17	100	0.030	8.1

TABLE 5

	Molybdenum (ppm)	Boron (wt%)	Antioxidant (wt%)	HTCT Deposit (mg)
Example 18	1,000	0.015	0.7	73.2
Example 19	1,000	0.030	0.7	15.6
Example 20	1,000	0.050	0.7	1.6
Example 21	1,000	0.080	0.7	1.3
Example 22	1,000	0.140	0.7	1.2
Example 23	1,000	0.015	1.4	69.8
Example 24	1,000	0.030	1.4	13.7
Example 25	1,000	0.050	1.4	1.3
Example 26	1,000	0.140	1.4	1.1

TABLE 6

	Molybdenum (ppm)	Boron (wt%)	Antioxidant (wt%)	HTCT Deposit (mg)
Example 27	1,000	0.015	0.7	81.6

TABLE 7

	Molybdenum (ppm)	Boron (wt%)	Antioxidant (wt%)	HTCT Deposit (mg)
Example 28	1,000	0.015	0.7	5.0

Claims

A lubricant oil composition produced by blending (A) a molybdenum-containing friction conditioner and (B) a boron-containing compound with a lubricant base oil, wherein the content of the molybdenum derived from the molybdenum-containing friction conditioner is 100 to 2,000 ppm (as the ratio by weight) and the content of the boron derived from the boron-containing compound is 0.015% by weight or more, to the total weight of the composition.
A lubricant oil composition produced by blending (A) a molybdenum-containing friction conditioner, (B) a boron-containing compound and (C) an antioxidant with a lubricant base oil, wherein the content of the molybdenum derived from the molybdenum-containing friction conditioner is 100 to 2,000 ppm (as the ratio by weight) and the content of the boron derived from the boron-containing compound is 0.015% by weight or more, to the total weight of the composition.
The lubricant oil composition of claim 2 wherein the anti-oxidant content is 0.05 to 5.0% by weight, to the total weight of the composition.
The lubricant oil composition of claim 2 or 3 wherein the anti-oxidant is phenol sulfide.
The lubricant oil composition of any preceding claim wherein the molybdenum-containing friction conditioner is sulfoxymolybdenum dithiocarbamate.
The lubricant oil composition of any preceding claim wherein the boron containing compound is selected from boron-containing succinimide, boron containing succinate ester, and mixtures thereof.