JP2002212579A - Reduced environmental load type lubricating oil composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an environmentally friendly lubricating oil composition significantly improving performances of heat resistance and cleaning ability under a condition continuously driven for a long time and reduced in amounts of chlorine compounds and sulfur compounds in the composition. SOLUTION: This lubricating oil composition is characterized by comprising 0.1-50 mass% of an alkaline earth metal salt of alkylsalicylate and having <=10 ppm of chlorine content therein measured by test method of ASTM D 6443.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention significantly improves heat resistance and cleanliness performance under conditions of continuous operation for a long time,
The present invention relates to an environmentally friendly lubricating oil composition having reduced chlorine and sulfur compounds in the composition.

[0002] The present invention relates to a lubricating oil composition in which the content of chlorine compounds and sulfur compounds in the composition is suppressed, and it is possible to suppress these compounds and oxides from the exhaust gas of an engine, The present invention relates to a lubricating oil composition that maintains excellent cleanliness for a long period of time under continuous operating conditions, and is a lubricating oil composition applicable to all marine internal combustion engines and land internal combustion engines. The present invention relates to a lubricating oil composition suitable for an internal combustion engine.

[0003]

2. Description of the Related Art Exhaust gas regulations arising from land-based internal combustion engines have been strictly regulated. Until now, air pollution from ships has been limited to terrestrial areas where humans live except for ports and coastal areas. It was not much of a problem because of the distance. However, in recent years, the problem of acid rain and the problem of global warming that destroy forests and lakes has become a serious issue that must be tackled on a global scale, and air pollutants from ships cannot be ignored. For this reason, the International Maritime Organization (IMO), one of the specialized agencies of the United Nations, has been around since 1990.
Regarding the prevention of air pollution from ships, which has been deliberated by the Marine Environment Protection Committee of “me Organization”, the “MARPOL 73/78 Convention (1973 on the International Convention for the Prevention of Ship Pollution in 1973, 1978)
The new Annex was adopted at the Conference of the Parties held in September 1997. The content of the regulation is that NOx should be manufactured with an engine whose emission amount is less than the regulation value, and that it should be checked through regular inspections. For SOx, the sulfur content in fuel oil should be regulated. It has become.

[0004] In ships, most of the main propulsion engines are diesel engines. Light oil and heavy oil, which are marine diesel engine fuels, contain a large amount of sulfur, and the exhaust gas emitted during combustion contains sulfur oxides (SOx). Further, nitrogen in the air is converted into nitrogen oxides (NOx) by combustion from the diesel engine, and is discharged as exhaust gas. Both sulfur oxides and nitrogen oxides are the causative agents of acid rain and must be reduced.

[0005] Exhaust gas contains water together with sulfur oxides, which react to produce sulfuric acid. A part of the produced sulfuric acid is included in the engine oil, and corrodes and wears the internal components of the engine. Therefore, at present, a relatively large amount of a basic metal-based detergent / dispersant is added to neutralize the sulfuric acid.

The particulate matter (P) contained in the exhaust gas
M) is causing a serious problem of environmental pollution. The United States Environmental Protection Agency provides Roger. O. McClellan and Fre
deric. J. Based on the research by Dr. Miller, P with a particle size of 2.5 μm or less, collectively referred to as PM2.5
M states that it is harmful to the human body. PM is composed of sulfate, soot, and soluble organic components (SOF) that are unburned components of fuel and lubricating oil due to sulfur content in fuel. It is said that the ratio of the SOF component to all PM is 30 to 40%. SOF oxidation catalyst for oxidizing and reducing SOF components and DP for filtering and reducing PM
Recently, these post-treatment devices are being installed in land-based diesel engines for the purpose of purifying exhaust gas.

However, if a relatively large amount of base oil or additive containing sulfur or chlorine is added to the engine oil, part of the engine oil is burned together with the fuel in the combustion chamber. A large amount of the compound will be contained in the exhaust gas. These sulfur oxides are not environmentally desirable, as they hinder the operation of the post-treatment device and are released as they are, affecting air pollution. However, to date, there are still many unknowns about the degree to which compounds originating from sulfur and chlorine in lubricating oils are released into the atmosphere, but this could lead to major problems in the future. Absent. In recent years, the invention of a marine engine oil composition has been disclosed in
Japanese Patent Application Laid-Open Nos. 1221081 and 10-121082 disclose an overbased alkaline earth metal phenate containing a large amount of sulfur, and do not discuss additives containing chlorine. A similar technique is disclosed in
JP-A-279980 and JP-A-10-287893, but a sulfur-containing antioxidant containing sulfur is compounded, and there is no discussion about additives containing chlorine. A part of the engine oil is burned together with the fuel in the combustion chamber, or is released into the atmosphere together with the exhaust gas as the engine oil itself. At that time, sulfur oxides and chlorine compounds will be included in the exhaust gas, and it is important to reduce the burden on the environment even a little in the future.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to significantly improve the heat resistance and cleanliness performance and reduce the chlorine compounds and sulfur compounds in the composition under the conditions of continuous operation for a long time. It is to provide an eco-friendly lubricating oil composition.

[0009]

Means for Solving the Problems The present inventors have conducted intensive studies in order to develop a formulation which serves as a basis for producing a lubricating oil composition which has solved the above-mentioned problems. With the use of a specific salicylate-based detergent and a specific base oil composition in combination with a lubricating oil composition for internal combustion engines (formulation formulation) under actual engine operating conditions without using The present inventors have found that it is possible to provide a lubricating oil having cleanliness over a long period of time, and have completed the present invention.

A first aspect of the present invention is that the composition contains 0.1 to 50% by mass of an alkylsalicylate alkaline earth metal salt and has a chlorine content (measured by ASTM D 6443 test method) of 10 ppm in a lubricating oil composition. The present invention relates to a lubricating oil composition characterized by the following.

The second aspect of the present invention is that the lubricating oil composition has a sulfur content (according to ASTM D5185 of 0.09 sulfur content).
The range of 〜0.60% is also a target, but in the present invention, the range of AST is higher than 0.60%.
(Measured by the method described in MD 5185).
The lubricating oil composition according to claim 1, which is 65% by mass or less.

The third aspect of the present invention is the amount of sulfated ash (JIS K
2272), wherein two or more alkaline earth metal salts of alkyl salicylates are used, and the sulfated ash content is 10%.
% By weight or less of the alkyl salicylate alkaline earth metal salt is 5% of the total alkyl salicylate alkaline earth metal salt.
3. The lubricating oil composition according to claim 1, wherein the lubricating oil composition accounts for 0% or more.

A fourth aspect of the present invention relates to the lubricating oil composition according to any one of claims 1 to 3, which contains a zinc dialkyldithiophosphate.

A fifth aspect of the present invention relates to the lubricating oil composition according to any one of claims 1 to 4, wherein the alkyl earth salicylate alkaline earth metal salt is an alkyl salicylate calcium salt.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION The alkaline earth metal salt of alkyl salicylate used in the lubricating oil composition of the present invention is described in Japanese Patent No. 12727115 owned by Shell Group,
As shown in No. 1031507, an oil-soluble basic salt of an aromatic carboxylic acid and a Group II metal of the periodic table having an atomic number of 12 to 56, which has a total base number of 12 mgKOH / g or more. It is. In addition, the total base number of the alkylsalicylate alkaline earth metal salt itself is 50 to 400 mgK.
OH / g is preferred as the additive for the lubricating oil composition of the present invention. In particular, the alkaline earth metal salt is preferably calcium or magnesium. As disclosed in JP-A-2000-63876, the alkyl salicylate magnesium salt has excellent cleaning performance even when the alkyl salicylate magnesium salt and the alkyl salicylate calcium salt are mixed and compounded, as in the case where only the alkyl salicylate calcium salt is compounded. It is known that the combination with the alkyl salicylate calcium salt has an excellent effect as long as the performance is not impaired.

The alkyl salicylate alkaline earth metal salt in the present invention is a mixture of an organic compound (1) and inorganic compounds (2) and (3) represented by the following formula.

Embedded image

In the above formula, R is an alkyl group, and preferably has an average alkyl chain length of 10 to 35 carbon atoms. If the average alkyl chain length is a short chain length of 10 or less carbon atoms, the dispersibility in oil is reduced and the cleanability is poor.
If the chain length is longer than 5, the acid neutralization performance is inferior. Also,
The chain length of the alkyl group of the organic compound is important in that the inorganic compound is stably dispersed in the lubricating oil, and the ability to neutralize the acidic substances formed in the lubricating oil due to oxidative deterioration is fully demonstrated. Has a role. Formulas (1) and (2)
M in (3) is an alkaline earth metal, preferably calcium, magnesium or barium, particularly preferably calcium. Alkyl salicylate alkaline earth metal salt, which is an organic compound represented by the formula (1),
It is preferable that the compound exists in such a form as to surround the nucleus composed of the inorganic compound represented by the formulas (2) and (3).

In the lubricating oil composition of the present invention, zinc dialkyldithiophosphate (ZnDTP) is preferably added as an antiwear agent. The addition of ZnDTP can prevent engine wear and oxidation of lubricating oil. The alkyl group of ZnDTP is not particularly limited, but usually preferably has 3 to 12 carbon atoms. The alkyl group preferably contains a secondary alkyl group (Sec-ZnDTP) and / or a primary alkyl group (Pri-ZnDTP) and / or an aryl group (Aryl-ZnDTP). Usually 0.3 to 5% by weight, preferably 1
~ 2% by weight. However, in applications where wear resistance is not required for engine parts, it is not necessary to add an antiwear agent to the lubricating oil composition.

The amount of the alkaline earth metal salt of alkyl salicylate used in the present invention is 1 to 50% by mass, preferably 2 to 45% by mass, assuming that the lubricating oil for an internal combustion engine as the final product is 100% by mass. % By mass. The lubricating oil composition specified in JIS K 2272 has a sulfated ash content of 0.1 to 10% by mass, preferably 0.1 to 10% by mass.
It is preferable to determine the amount of these salicylate metal salts to be adjusted so as to be 2 to 9% by mass.

[0020] The amount of sulfated ash is determined by adding a metal-based detergent additive (such as an alkyl salicylate calcium salt) contained in the lubricating oil.
The ash content is determined by adding sulfuric acid to the carbonized residue generated by burning the sample and quantitatively expressing it as a sulfate (Test method: JIS K2272). In general, it is said that if the content of sulfated ash is large, good results can be obtained in a high-temperature detergency test represented by a hot tube test (because the amount of a metal-based detergent added inevitably increases).

The sulfur content is mainly due to the base oil and the antiwear agent. However, some metal-based detergents contain sulfur in the structural formula thereof. For example, calcium alkylsulfonate (metallic detergent C in the specification) and alkyl finate calcium salt (in the specification) The metallic detergent D) contains sulfur,
The alkaline earth metal salt of alkyl salicylate used in the present invention is substantially free of sulfur.

The ashless dispersant is usually used in an amount of 0.1 to 20% by mass.
And the types thereof are described in Japanese Patent Nos. 1366796 and 166, which are owned by Shell Group.
And polyalkenyl succinimides and polyalkenyl succinates described in Nos. 7140, 1302811 and 1743435. It is preferable to use a polyalkenyl succinimide or a polyalkenyl succinic ester having a nitrogen content of less than 1.6%. This is because an ashless dispersant having a low nitrogen content is preferable in terms of performance. In fact, in the past, ashless dispersants with a high nitrogen content were generally said to be good for diesel engines, and they have been used in recent years. Ashless dispersants have also begun to be marketed. The polyalkenyl succinimide is obtained by reacting alkenyl succinic anhydride or alkenyl succinic anhydride with a polyamine. It is preferable to formulate so that the nitrogen content in the lubricating oil composition is not less than 0.01%, but it is preferable that the content is not more than 0.3% at the maximum. If at least 0.01% is not contained, soot mixed in the lubricating oil and generated sludge may not be maintained in a stable dispersed state.

As the antioxidant, for example, 2,6-di-
t-butylphenol, 4,4'-methylenebis-
Phenolic antioxidants such as (2,6-di-t-butylphenol); and amine antioxidants such as alkylated diphenylamine, phenyl-α-naphthylamine, and alkylated-α-naphthylamine. It can be used at a rate of 0.01 to 2% by mass.

It is also effective to add an appropriate amount of other various additives to the lubricating oil composition of the present invention, if desired. As other additives, depending on the purpose, pour point depressants, defoamers, rust inhibitors, demulsifiers (used to break the emulsion and separate it into two liquid phases), metal deactivators, Viscosity index improvers may be used. Examples of pour point depressants include Japanese Patent Nos. 1195542 and 1264056.
For example, polymethacrylates described in No. 1 are used. As an antifoaming agent, silicone, fluorosilicone, fluoroalkyl ether, dimethylpolycyclohexane, polyacrylate and the like are used. As the rust preventive, petroleum sulfonate, alkylbenzene sulfonate, dinonylnaphthalene sulfonate, alkenylsuccinic acid or its ester derivative, polyhydric alcohol ester, benzotriazole-based compound, thiadiazole-based compound and the like are used. As the demulsifier, a polyalkylene glycol-based nonionic surfactant such as polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, and polyoxyethylene alkyl naphthyl ether is used. As the metal deactivator, imidazoline, pyrimidine derivative, alkyl thiadiazole, mercaptobenzothiazole, benzotriazole or a derivative thereof, mercaptobenzothiazole, thiadiazole or a derivative thereof, benzimidazole or a derivative thereof, propionnitrile or a derivative thereof are used. . As a viscosity index improver, based on 100 parts by weight of a lubricating oil composition for an internal combustion engine,
0.01 to 20 parts by weight is blended. Examples of viscosity index improvers include Japanese Patent Nos. 9554077, 1031507 and 14687 owned by Shell Group.
No. 52, No. 1764494, No. 1751082, styrene-butadiene copolymer, styrene-isoprene star copolymer, polymethacrylate, ethylene-propylene copolymer, and the like. It is used at a ratio of 1 to 20% by mass. In addition, a dispersion type viscosity index improver obtained by copolymerizing a polar monomer containing a nitrogen atom or an oxygen atom in a molecule thereof can also be used in the same manner.

One of the reasons why the lubricating oil composition of the present invention has excellent detergency and heat resistance lies in the technique of formulating a lubricating oil composition that suppresses the formation of sulfate ions. As is generally known, sulfate ions generated in lubricating oil are generated by combustion of sulfur compounds contained in fuel and deterioration of additives containing sulfur element contained in lubricating oil compositions of internal combustion engines. It is possible. Alkyl salicylate metal salt, which is the main lubricating oil composition of the present invention, does not contain this sulfur element which generates sulfate ions in the compound, and has a compounding formula capable of suppressing the formation of sulfate ions. It is considered that the activity of the additive can be suppressed and the function of the additive itself can be promoted, and it is possible to enhance the cleanliness and the acid neutralizing ability. The lubricating oil composition of the present invention exhibits excellent performance as a lubricating oil not only for marine diesel engines but also for land-based automobile engines and engines using gas fuel. In particular, from the perspective of generally reusing used lubricating oil of land-based vehicle engine oil as a fuel, it is very important from the viewpoint of environmental protection to contain sulfur and chlorine compounds as little as possible. come.

The lubricating oil composition of the present invention has the ability to quickly neutralize acidic components such as sulfurous acid generated at the time of combustion and disperses combustion residues, and to the piston liner or piston ring groove in the combustion chamber of the engine. An environmental load-reducing lubricating oil composition for internal combustion engines that has an excellent ability to prevent the accumulation of water and keep it clean.

[0027]

EXAMPLES The present invention will be described below with reference to examples and comparative examples, but the present invention is not limited to only these examples. Each engine oil composition having the composition shown in Table 1 was prepared and their performance evaluation tests were performed. Table 1 shows the test results.

<Hot Tube Test> The heat resistance and cleanliness of the test oil were evaluated using a hot tube tester test device (manufactured by Komatsu Engineering Co., Ltd.). This device evaluates the high temperature cleanliness of engine oil by the lacquer concentration of glass test tubes. For the test method, see JPI-5S-
According to the procedure specified in 55-99 (engine oil-hot tube test method), evaluation was performed by Method A (scoring method). As for the result of cleanliness, as defined in the test method, the worst case is 0 point (black case) and the best 10 point (colorless and transparent).

The base oil compositions of all test oils were based on standard engine oil compositions. The total base number value closely related to the cleaning performance under high temperature is 40 mg KO for each sample oil.
H / g. The base oils A to C in the examples and comparative examples have the following types and properties.

Base oil A: kinematic viscosity at 100 ° C. is 17.6 mm ²
/ S, kinematic viscosity at 40 ° C is 138.0 mm ² / s, viscosity index 140, pour point -27 ° C, flash point 300 ° C, and pentaerythritol hindered ester having properties of 1% by weight of evaporation loss. A synthetic base oil of a polyol ester compound was used.

Base oil B: kinematic viscosity at 100 ° C. 8.15 mm²
/ S, kinematic viscosity at 40 ° C is 47.9 mm ²/ S, viscosity index 1
44, high viscosity of pour point -20 ° C, flash point 260 ° C
An index base oil was used.

The high viscosity index base oil is a raw wax (slack wax) separated by solvent dewaxing, which is subjected to hydrogenolysis (catalytic cracking) in the presence of a catalyst to produce linear paraffin. Viscosity index of 130 or more (typically 140 to 1) obtained by isomerization to branched paraffin.
55) or hydrogen and carbon monoxide obtained by a gasification process (partial oxidation) of natural gas (methane or the like) having natural gas (methane or the like) as raw materials to obtain heavy linear paraffins by Fischer-Tropsch polymerization. A lubricating base oil having a viscosity index of 130 or more (typically 140 to 155) obtained by the same catalytic cracking isomerization as described above may be mentioned, but the base oil used here is limited to either one. Not something.

Base oil C: A mineral base oil containing 0.40% by mass of sulfur in a solvent refined base oil or a hydrogenated refined base oil alone or as a mixture. The base oil viscosity was adjusted so as to be SAE (American Society of Automotive Engineers) 40 grade. The SAE 40 grade has a kinematic viscosity at 100 ° C. in a viscosity range of 12.5 to 16.3 mm ² / s.

The properties of the base oil used in the present invention are at 100 ° C.
Kinematic viscosity is 2-80mm²/ S, preferably 4 to 50
mm²/ S. Here, the kinematic viscosity at 100 ° C. is 2
mm ²If it is less than / s, the lubricity decreases and the seizure resistance decreases.
Inferior, also 80mm²/ S or more inside the engine
Of the increase in resistance due to the viscous
Not preferred from the point.

The viscosity index of the base oil used in the present invention is 75 or more, preferably 80 or more. Viscosity index 7
If it is less than 5, it is not preferable as the base oil of the lubricating oil composition for an internal combustion engine of the present invention because of poor startability at low temperatures and poor lubricity due to a decrease in viscosity at high temperatures.

All test oil additive compositions were based on standard marine lubricating oil additive compositions. That is, a metal detergent, an ashless dispersant, an antifoaming agent, and the like are blended.

In particular, for metal detergents, alkyl salicylate calcium salt, alkyl sulfonate calcium salt and alkyl finate calcium salt were used. The additives of the metal-based detergents A to D in the examples have the following properties. Metallic detergent A (alkyl salicylate calcium salt): total base number (hydrochloric acid method) 160 mg KOH / g, total base number (perchloric acid method) 170 mg KOH / g, sulfated ash 2
0.4% metal detergent B (alkyl salicylate calcium salt): total base number (hydrochloric acid method) 69 mg KOH / g, total base number (perchloric acid method) 70 mg KOH / g, sulfate ash content 8.6
% By mass Metallic detergent C (alkyl sulfonate calcium salt): total base number (hydrochloric acid method) 292 mg KOH / g, total base number (perchloric acid method) 300 mg KOH / g, sulfated ash content 4
0.8% by mass metal-based detergent D (calcium alkyl finate):
Total base number (hydrochloric acid method) 250 mg KOH / g, total base number (perchloric acid method) 254 mg KOH / g, sulfated ash 30.
9% by mass

Zinc dialkyldithiophosphate as an antiwear agent has a primary alcohol residue and a main component having 4 to 6 carbon atoms.
It is a commercial product containing a primary alcohol residue as a main component. 1
Zinc dialkyldithiophosphate having a primary component as a main component is preferably used as an antiwear agent in a marine lubricating oil composition because of its excellent thermal stability. Not a thing.

[0039]

[Table 1]

Comparing Example 1 with Comparative Examples 1 and 2, it can be seen that, in the formulation using the same base oil C, the alkyl salicylate calcium salt has better detergency than the alkyl sulfonate calcium salt and the alkyl fininate calcium salt. You can see that he has the ability. Comparing the chlorine contents at that time, it can be seen that those having a low chlorine content have excellent cleanability. Comparing Example 1 and Example 2 with Comparative Example 3, the one with clearly lower chlorine content is superior. Those containing a calcium salt of an alkyl salicylate and having a lower chlorine content have better detergency. The representative properties in the table naturally represent the properties of the lubricating oil compositions of the respective examples and comparative examples. The total base numbers in the table are adjusted to 40 mgKOH / g by adjusting the mixing ratio of each additive. The reason why the values of the total base numbers are uniform is that the oil having a high total base number also has a high sulfated ash content and a high high-temperature cleaning performance. Therefore, it is not an exaggeration to say that the value of the total base number determines the commercial value when selling as a commercial product. Particularly in the marine engine oil business, the value of the total base number is very important in predicting the performance of the lubricating oil. Therefore, by keeping the total base number constant,
This shows that, even if the total base numbers are the same, if the other blending conditions are different, a large difference in performance appears.

In Example 3, even when the same combination of the metal detergent and the alkylsalicylate calcium salt as in Example 1 was used, a difference in performance was remarkable in a blended system with a synthetic base oil containing no sulfur. You can see that. Comparing Example 3 and Example 4, when the sulfur content (attributable to the antiwear agent) is such that 1% of the antiwear agent is added,
It can be seen that there is no effect on the performance at high temperatures. It can be said that an anti-wear agent can be added as necessary, but it is preferable not to add it. From the above, a blended oil having a low sulfur content in the lubricating oil composition and containing a calcium salt of an alkyl salicylate and having a low chlorine content has excellent detergency.

Examples 3 and 4 were carried out by balancing the mixing ratio of two or more alkylsalicylate calcium salts of a metal detergent to the base oil component consisting of base oil A and base oil B. Example 3 and Example 4 correspond to Example 1 and Example 2
It can be seen that the composition has a high cleaning ability that surpasses the performance of the compounded oil. Further, when comparing Example 1 and Example 2, it is clear that both of them have excellent cleanliness in terms of performance, but they have a low level of sulfated ash. Example 2 with salt may be more advantageous. The value of sulfated ash is the ash measured by weighing inorganic substances mainly as sulfates. The difference in the cleaning performance despite the fact that the sulfated ash value in the lubricating oil composition is almost the same is because the organic substances contained in the metallic detergent B are stable in oil at high temperatures. And disperse,
It is considered that the cleaning performance was enhanced. From the above, it can be said that the alkyl salicylate calcium salt having a lower sulfated ash content is more excellent in high-temperature cleaning performance.

[0043]

According to the present invention, there is provided a lubricating oil composition in which the content of chlorine compounds and sulfur compounds in the composition is suppressed, and the heat resistance and cleanability are greatly improved under the conditions of continuous operation for a long time. And reduced the environmental burden.

[Brief description of the drawings]

FIG. 1 is a view schematically showing a hot tube tester used for evaluating the cleanliness of a lubricating oil composition.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C10N 20:00 C10N 20:00 Z 30:00 30:00 Z 30:04 30:04 30:06 30: 06 30:08 30:08 40:25 40:25

Claims (5)

[Claims] Claims 1. An alkylsalicylate alkaline earth metal salt containing 0.1 to 50% by mass and a chlorine content (measured by ASTM D 6443 test method) of 10% or less in a lubricating oil composition. A lubricating oil composition characterized by the following: 2. The sulfur content in a lubricating oil composition (ASTM)
The lubricating oil composition according to Claim 1, wherein the lubricating oil composition (D5185) is 0.65% by mass or less. 3. An alkylsalicylate alkaline earth metal salt having a sulfated ash content of 10% by mass or less, wherein two or more alkylsalicylate alkaline earth metal salts having different sulfated ash contents (according to JIS K 2272) are used. The lubricating oil composition according to claim 1 or 2, wherein the composition accounts for 50% or more of the salicylate alkaline earth metal salt. 4. The lubricating oil composition according to claim 1, which comprises a zinc dialkyldithiophosphate. 5. The lubricating oil composition according to claim 1, wherein said alkyl salicylate alkaline earth metal salt is an alkyl salicylate calcium salt.