MARINE LUBRICATING OIL COMPOSITE ADDITIVE

Abstract

The present invention relates to a marine lubricating oil composite additive. Based on the total weight of the composite additive, said marine lubricating oil composite additive comprises: 25-45% sulfonate detergent with superhigh base number, 40-60% phenolate detergent with low base number, 0-8% dispersing agent, 0-4% antiwear agent, and 10-20% Group I base oil with high viscosity index which is selected from the group consisting of 400SN, 500SN and 600SN. The composite additive according to the present invention can satisfy the requirement of BOB system about the viscosity and base number, and can be blended with many system oils under a number of domestic and foreign brands so as to provide cylinder lubricating oils with different base numbers. The composite additive according to the present invention has good adaptability and excellent performances in terms of antiwear, antioxidization and high temperature detergency, which meet the requirement of marine engines about the performance of cylinder lubricating oils. Moreover, the composite additive according to the present invention is able to maintain good stability in the base oil of the system oil as well as good compatibility, and thus the lubricating performance of the cylinder lubricating oil will not be adversely affected.

Description

CLAIM OF PRIORITY

[0001] This application is a divisional of and claims the benefit of priority to U.S. patent application Ser. No. 13/416,073, filed Mar. 9, 2012, which claims the benefit of priority of Chinese Patent Application 201110057541.4, filed on Mar. 10, 2011, which applications are incorporated by reference as if reproduced herein and made a part hereof in their entirety, and the benefit of priority of each of which is claimed herein.

FIELD OF THE INVENTION

[0002] The present invention relates to a composite additive used for marine lubricating oils, and more particularly to a composite additive designed for cylinder lubricating oils which is applied in shipborne BOB systems.

BACKGROUND OF THE INVENTION

[0003] The current BOB (Blender-on-Board) online blending system equipped on ocean vessels is an automatic control system that blends the marine system oil with a composite additive which is designed for the marine lubricating oils in the BOB system so as to provide a cylinder lubricating oil that have an optional target base number, and such cylinder lubricating oil can be rapidly transferred to the engine in order to meet the different requirements for the base number of the cylinder lubricating oil in cases of using fuels with different sulfur contents. A schematic diagram for the operating principle of BOB online blending system is shown in FIG. 1.

[0004] The operating procedure of the BOB system is as follows: the system oil is pumped from the main oil tank to each lubrication point of the engine so as to provide lubrication and thereafter recycled back to the main oil tank, wherein part of the system oil is side-drawn and then blended with a composite additive in the BOB blending device to form a cylinder oil with required base numbers, which is burned off after fulfilling lubrication, and the residue thereof flows into a waste oil tank.

[0005] The composite additives designed for the BOB system are remarkably different from the traditional marine lubricating oils. The later are lubricating oil products with fixed base numbers, which are produced in blending plants and may be directly used by adding into the oil tank of vessels, whereas the former are additives produced by blending plants and blended with the system oil before adding into a tank of vessels so as to provide marine cylinder lubricating oils with different base numbers in order to meet the requirement of the use in engines.

[0006] Therefore, the composite additives designed for the BOB system have several features in terms of the technical requirement:

[0007] 1. Sufficient antiwear and antioxidization properties should be preserved when relatively low dosage is used;

[0008] 2. Good compatibility to system oils under different brands;

[0009] 3. The composite additive should satisfy the requirement of being pumped within the BOB system and fit with the blending system.

[0010] According to the novelty search within Chinese and worldwide patents, no related reference documents are found in the field of both shipborne BOB online blending system and the composite additive designed the BOB system.

[0011] In the light of the disclosure reported by related Chinese and worldwide patents, it is known that the binary detergent system composed by a sulfonate detergent and a phenolate detergent is widely used in the formulation of the cylinder oil at present. Meanwhile, the above two primary additives of sulfonate and phenolate detergents are both easy to purchase and cheap in price in the international market. With an aim to the world market of the marine lubricating oil, the establishment of an international blending and supplying network can, on one hand, expand the oil supplying network of PetroChina and improve the sale and service level, and can benefit to reducing the production cost so as to sharpen the competitive edge of self-owned brand products of PetroChina.

SUMMARY OF THE INVENTION

[0012] The purpose of the present invention is to provide a marine lubricating oil composite additive that can not only satisfy the requirement of the marine BOB online blending system but also have wide adaptability.

[0013] The marine lubricating oil composite additive is characterized in that based on the total weight of the composite additive, it comprises: 25-45% sulfonate detergent with superhigh base number, 40-60% phenolate detergent with low base number, 0-8% dispersing agent, 0-4% antiwear agent, and 10-20% Group I base oil with high viscosity index.

[0014] Said sulfonate detergent with superhigh base number is C₂₂-C₃0 linear alkyl benzene calcium sulphonate, wherein the base number thereof is 395-430 mgKOH/g.

[0015] Said phenolate detergent with low base number is C₂₀-C₂5 alkyl sulfurized calcium phenolate, wherein the base number thereof is 240-265 mgKOH/g.

[0016] Said dispersing agent is selected from the group consisting of mono-polyisobutylene succinimide, bis-polyisobutylene succinimide and multi-polyisobutylene succinimide.

[0017] Said antiwear agent is zinc long-chain alkyl thiophosphate with the structure corresponding to the following formula,

##STR00001##

[0018] wherein R₁, R₂, R₃ and R₄ are long-chain primary alkyl groups each comprising 12-18 carbon atoms, or R₁, R₂, R₃ and R₄ are long-chain secondary alkyl groups each comprising 12-16 carbon atoms.

[0019] Said base oil is Group I base oil with high viscosity index which is selected from the group consisting of 400SN, 500SN and 600SN, the kinematic viscosity of which is 8.5-11.5 cst at 100° C. The appropriate base oils are commercially available from PetroChina Company.

[0020] The marine lubricating oil composite additive according to the present invention employs two composed detergents supplemented by antiwear agent and dispersing agent, and takes advantage of not only the excellent detergency and dispersion performance of the sulfonate detergent with superhigh base number but also the excellent antiwear and antioxidization performance of the phenolate detergent with low base number. The formulation of composite additive is optimized so as to satisfy the requirement of the BOB online blending system.

[0021] The technical features of the present invention are as follows: the requirement of BOB system process for the viscosity and base number can be satisfied; the composite additive according to the present invention is compatible with many system oils under typical foreign brands, and the formulated cylinder lubricating oils with different base numbers have excellent performances in terms of antiwear, antioxidization and high temperature detergency. The present composite additive has been tested by sailing over 4000 hours, and has been technically certified by MAN B&W, the engine OEM (original equipment manufacturer).

DESCRIPTION OF DRAWINGS

[0022] FIG. 1 shows a schematic diagram for the operating principle of BOB online blending system.

[0023] FIG. 2 shows the monitoring data for samples of the fresh/waste cylinder oils using the composite additive of the present application during the sailing.

DETAILED DESCRIPTION OF THE INVENTION

Example 1

[0024] The composite additive used in BOB system may be prepared from the components mentioned below (their contents in weight percentage are also given in detail) by means of normal process. The blending process is as follows: the base oil is firstly added into a blending barrel/tank, and then the temperature is raised to 65±5° C., wherein the base oil should have a kinematic viscosity of 7.0-12.0 mm²/s at 100° C.; the antiwear agent, the dispersing agent and the detergents are subsequently introduced into said blending barrel/tank, and stirring is carried out at 65±5° C. for 2 hours until completely homogeneous. The above process is implemented in every example hereafter.

[0025] In this example, the sulfonate with superhigh base number is calcium long-chain linear alkyl benzene sulphonate with superhigh base number wherein the long-chain linear alkyl group comprises 22 carbon atoms, and the base number thereof is 430 mgKOH/g. The sulfurized alkyl phenolate with low base number is sulfurized calcium long-chain alkyl phenolate wherein the alkyl group comprises 25 carbon atoms, and the base number thereof is 240 mgKOH/g. The antiwear agent is zinc long-chain primary alkyl thiophosphate wherein the long-chain primary alkyl group comprises 12 carbon atoms. The dispersing agent is bis-polyisobutylene succinimide. The base oil is group I base oil 600SN available from PetroChina Daqing Petrochemical Company.

TABLE-US-00001 Contents Components (%) Linear alkyl (C22) calcium sulfonate with superhigh base number 25 Sulfurized calcium alkyl (C25) phenolate with low base number 55 Zinc primary alkyl (C12) thiophosphate 2 Bis-polyisobutylene succinimide 8 Group I base oil of 600SN 10

Example 2

[0026] The composite additive used in BOB system may be prepared from the components mentioned below (their contents in weight percentage are also given in detail) by means of normal process.

[0027] In this example, the sulfonate with superhigh base number is calcium long-chain linear alkyl benzene sulphonate with superhigh base number wherein the long-chain linear alkyl group comprises 30 carbon atoms, and the base number thereof is 395 mgKOH/g. The sulfurized alkyl phenolate with low base number is sulfurized calcium long-chain alkyl phenolate wherein the alkyl group comprises 20 carbon atoms, and the base number thereof is 265 mgKOH/g. The antiwear agent is zinc long-chain secondary alkyl thiophosphate wherein the long-chain secondary alkyl group comprises 16 carbon atoms. The dispersing agent is multi-polyisobutylene succinimide. The base oil is group I base oil 500SN available from PetroChina Daqing Petrochemical Company.

TABLE-US-00002 Contents Components (%) Linear alkyl (C30) calcium sulfonate with superhigh base number 45 Sulfurized calcium alkyl (C20) phenolate with low base number 41 Zinc secondary alkyl (C16) thiophosphate 4 Multi-polyisobutylene succinimide 0 Group I base oil of 500SN 10

Example 3

[0028] The composite additive used in BOB system may be prepared from the components mentioned below (their contents in weight percentage are also given in detail) by means of normal process.

[0029] In this example, the sulfonate with superhigh base number is calcium long-chain linear alkyl benzene sulphonate with superhigh base number wherein the long-chain linear alkyl group comprises 22 carbon atoms, and the base number thereof is 430 mgKOH/g. The sulfurized alkyl phenolate with low base number is sulfurized calcium long-chain alkyl phenolate wherein the alkyl group comprises 25 carbon atoms, and the base number thereof is 250 mgKOH/g. The antiwear agent is zinc long-chain primary alkyl thiophosphate wherein the long-chain primary alkyl group comprises 18 carbon atoms. The dispersing agent is bis-polyisobutylene succinimide. The base oil is group I base oil 400SN available from PetroChina Daqing Petrochemical Company.

TABLE-US-00003 Contents Components (%) Linear alkyl (C22) calcium sulfonate with superhigh base number 32 Sulfurized calcium alkyl (C25) phenolate with low base number 40 Zinc primary alkyl (C18) thiophosphate 0 Bis-polyisobutylene succinimide 8 Group I base oil of 400SN 20

Example 4

[0030] The composite additive used in BOB system may be prepared from the components mentioned below (their contents in weight percentage are also given in detail) by means of normal process.

[0031] In this example, the sulfonate with superhigh base number is calcium long-chain linear alkyl benzene sulphonate with superhigh base number wherein the long-chain linear alkyl group comprises 22 carbon atoms, and the base number thereof is 430 mgKOH/g. The sulfurized alkyl phenolate with low base number is sulfurized calcium long-chain alkyl phenolate wherein the alkyl group comprises 25 carbon atoms, and the base number thereof is 240 mgKOH/g. The antiwear agent is zinc long-chain primary alkyl thiophosphate wherein the long-chain primary alkyl group comprises 12 carbon atoms. The dispersing agent is bis-polyisobutylene succinimide. The base oil is group I base oil 400SN available from PetroChina Daqing Petrochemical Company.

TABLE-US-00004 Contents Components (%) Linear alkyl (C22) calcium sulfonate with superhigh base number 28 Sulfurized calcium alkyl (C25) phenolate with low base number 60 Zinc primary alkyl (C12) thiophosphate 2 Bis-polyisobutylene succinimide 0 Group I base oil of 400SN 10

Example 5

[0032] The composite additive used in BOB system may be prepared from the components mentioned below (their contents in weight percentage are also given in detail) by means of normal process.

[0033] In this example, the sulfonate with superhigh base number is calcium long-chain linear alkyl benzene sulphonate with superhigh base number wherein the long-chain linear alkyl group comprises 30 carbon atoms, and the base number thereof is 410 mgKOH/g. The sulfurized alkyl phenolate with low base number is sulfurized calcium long-chain alkyl phenolate wherein the alkyl group comprises 25 carbon atoms, and the base number thereof is 265 mgKOH/g. The antiwear agent is zinc long-chain primary alkyl thiophosphate wherein the long-chain primary alkyl group comprises 18 carbon atoms. The dispersing agent is multi-polyisobutylene succinimide The base oil is group I base oil 600SN available from PetroChina Daqing Petrochemical Company.

TABLE-US-00005 Contents Components (%) Linear alkyl (C30) calcium sulfonate with superhigh base number 30 Sulfurized calcium alkyl (C25) phenolate with low base number 45 Zinc primary alkyl (C18) thiophosphate 4 Multi-polyisobutylene succinimide 6 Group I base oil of 600SN 15

Example 6

[0034] The composite additive used in BOB system may be prepared from the components mentioned below (their contents in weight percentage are also given in detail) by means of normal process.

[0035] In this example, the sulfonate with superhigh base number is calcium long-chain linear alkyl benzene sulphonate with superhigh base number wherein the long-chain linear alkyl group comprises 22 carbon atoms, and the base number thereof is 410 mgKOH/g. The sulfurized alkyl phenolate with low base number is sulfurized calcium long-chain alkyl phenolate wherein the alkyl group comprises 20 carbon atoms, and the base number thereof is 300 mgKOH/g. The antiwear agent is zinc long-chain secondary alkyl thiophosphate wherein the long-chain secondary alkyl group comprises 12 carbon atoms. The dispersing agent is mono-polyisobutylene succinimide The base oil is Group I base oil 500SN available from PetroChina Daqing Petrochemical Company.

TABLE-US-00006 Contents Components (%) Linear alkyl (C22) calcium sulfonate with superhigh base number 40 Sulfurized calcium alkyl (C20) phenolate with low base number 40 Zinc secondary alkyl (C12) thiophosphate 1 Mono-polyisobutylene succinimide 4 Group I base oil of 500SN 15

Example 7

[0036] The composite additive used in BOB system may be prepared from the components mentioned below (their contents in weight percentage are also given in detail) by means of normal process.

[0037] In this example, the sulfonate with superhigh base number is calcium long-chain linear alkyl benzene sulphonate with superhigh base number wherein the long-chain linear alkyl group comprises 22 carbon atoms, and the base number thereof is 430 mgKOH/g. The sulfurized alkyl phenolate with low base number is sulfurized calcium long-chain alkyl phenolate wherein the alkyl group comprises 25 carbon atoms, and the base number thereof is 240 mgKOH/g. The antiwear agent is zinc long-chain primary alkyl thiophosphate wherein the long-chain primary alkyl group comprises 18 carbon atoms. The dispersing agent is bis-polyisobutylene succinimide. The base oil is group I base oil 400SN available from PetroChina Daqing Petrochemical Company.

TABLE-US-00007 Contents Components (%) Linear alkyl (C22) calcium sulfonate with superhigh base number 32 Sulfurized calcium alkyl (C25) phenolate with low base number 58 Zinc primary alkyl (C18) thiophosphate 0 Bis-polyisobutylene succinimide 0 Group I base oil of 400SN 10

[0038] The present invention provides a bis-detergent composite additive designed for the BOB system, and the physical and chemical properties of such composite additive are able to satisfy the requirement of Maersk Fluid Co. about the composite additive designed for the BOB system. The physical and chemical properties of the composite additives obtained by the above examples are listed in Table 1.

TABLE-US-00008 TABLE 1 Comparison of the physical and chemical properties of the bis-detergent cylinder oil composite additives designed for the BOB system Sample Example Example Example Example Example Example Example Technical Item 1 2 3 4 5 6 7 requirement Method Kinematic 81.68 90.46 85.38 86.72 92.36 86.46 88.69 ≦95 GB/T 265 viscosity according (100° C.), mm²/s to OEM Base number, 305 295 310 290 292 302 298 ≧285 .sup. SH/T 0251 mgKOH/g according to OEM Density (20° C.), 1097.6 1085.5 1072.0 1095.0 1079.6 1105.4 1092.6 Report .sup. SH/T 0604 kg/m³ Flash point 185 186 192 178 184 198 186 ≧150 GB/T 261 (closed), ° C. Moisture, % 0.18 0.03 0.06 0.08 0.03 0.06 0.03 ≦0.2 GB/T 260 Mechanical 0.032 0.012 0.020 0.030 0.018 0.028 0.032 ≦0.1 GB/T 511 impurity, % Sulfated ash, % 32.96 36.68 38.42 37.61 34.98 35.29 30.64 Report GB/T 2433

[0039] The composite additive designed for the BOB system using double detergents provided by the present invention is well compatible with system oil products under typical domestic and foreign brands, for example Exxon-Mobile Company, BP Company and PetroChina. The performances of the formulated cylinder oils with different base numbers are individually studied by simulated experiments, and the results demonstrate that the cylinder oils with different base numbers maintain good combination property as for lubricating oil, for example the antioxidization, antiwear, detergency and water resisting performances and etc.

[0040] Herein, the antioxidization performance of the cylinder oil is evaluated according to the oxidative induction time which is measured by differential scanning calorimetry (PDSC). The antiwear performance is evaluated by the Pb value and the long wear extent which are obtained by four-ball test. The coking tests are carried out in order to test the detergency performance of the cylinder oil, while the gel tests are carried out so as to test the storage stability.

[0041] The bis-detergent composite additive designed for the BOB system formulated according to the formulation of Example 6 is blended with Exxon-Mobile system oil Mobilgard M300, BP system oil Energol OE-HT30 and Kunlun system oil DCC3008, respectively, so as to provide cylinder oils with the base numbers of 70 mgKOH/g, 60 mgKOH/g, 50 mgKOH/g and 40 mgKOH/g as shown in Tables 2, 3, 4 and 5.

TABLE-US-00009 TABLE 2 Physical and chemical properties of the cylinder oil with the base number of 70 mgKOH/g and the simulated performance thereof Mobilgard Energol KUNLUN Item Unit M300 OE-HT30 DCC3008 Method Dosage of the 22 22 21.2 composite additive, % Viscosity, 100° C. mm²/s 13.77 14.23 13.37 GB/T 265 Viscosity -- 103 105 100 ISO2909 coefficient Base number mgKOH/g 69.7 69.4 69.4 SH/T 0251 Flash point ° C. 258 252 250 GB/T 261 Sulfated ash, % w % 7.49 7.85 7.38 GB/T 2433 Oxidative min 15.13 15.06 13.24 SH/T 0719, the test condition induction time by is: 200° C., 3.0 MPa, O₂ PDSC Pb value by N 1254 1186 1186 GB/T 3142 four-ball test Long wear extent mm 0.33 0.34 0.33 SH/T 0189 by four-ball test Coking test mg 12 18 16 SH/T 0300 Gel test ml 0.5 0.25 0.1 1% of water and 99% of oil are blended in the test tube, stirred by an agitator blade (2000 rpm) for 60 sec and stored at 70° C. for 96 h. The precipitation amount at tube bottom is observed.

TABLE-US-00010 TABLE 3 Physical and chemical properties of the cylinder oil with the base number of 60 mgKOH/g and the simulated performance thereof Mobilgard Energol KUNLUN Item Unit M300 OE-HT30 DCC3008 Method Dosage of the 18.64 18.64 17.8 composite additive, % Viscosity, 100° C. mm²/s 13.26 13.70 12.82 GB/T 265 Viscosity coefficient -- 103 105 102 ISO2909 Base number mgKOH/g 69.6 69.7 60.5 SH/T 0251 Flash point ° C. 254 254 258 GB/T 261 Sulfated ash, % w % 7.10 7.28 7.05 GB/T 2433 PDSC min 13.20 14.22 12.83 SH/T 0719, the test condition is: 200° C., 3.0 MPa, O₂ Pb value by four-ball N 1186 1117 1186 GB/T 3142 test Long wear extent by mm 0.34 0.35 0.34 SH/T 0189 four-ball test Coking test mg 16 22 9 SH/T 0300 Gel test ml 0.3 0.3 0.2 1% of water and 99% of oil are blended in the test tube, stirred by an agitator blade (2000 rpm) for 60 sec and stored at 70° C. for 96 h. The precipitation amount at tube bottom is observed.

TABLE-US-00011 TABLE 4 Physical and chemical properties of the cylinder oil with the base number of 50 mgKOH/g and the simulated performance thereof Mobilgard Energol KUNLUN Item Unit M300 OE-HT30 DCC3008 Method Dosage of the 15.25 15.25 14.38 composite additive, % Viscosity, 100° C. mm²/s 12.89 13.36 12.36 GB/T 265 Viscosity coefficient -- 101 105 101 ISO2909 Base number mgKOH/g 49.5 49.4 49.3 SH/T 0251 Flash point ° C. 252 260 252 GB/T 261 Sulfated ash, % w % 6.83 6.78 6.62 GB/T 2433 PDSC min 12.98 13.68 12.22 SH/T 0719, the test condition is: 200° C., 3.0 MPa, O₂ Pb value by four-ball N 1117 1049 1117 GB/T 3142 test Long wear extent by mm 0.34 0.35 0.35 SH/T 0189 four-ball test Coking test mg 19 26 12 SH/T 0300 Gel test ml 0.5 0.45 0.35 1% of water and 99% of oil are blended in the test tube, stirred by an agitator blade (2000 rpm) for 60 sec and stored at 70° C. for 96 h. The precipitation amount at tube bottom is observed.

TABLE-US-00012 TABLE 5 Physical and chemical properties of the cylinder oil with the base number of 40 mgKOH/g and the simulated performance thereof Mobilgard Energol KUNLUN Item Unit M300 OE-HT30 DCC3008 Method Dosage of the 11.86 11.86 10.96 composite additive, % Viscosity, 100° C. mm²/s 12.56 12.89 11.98 GB/T 265 Viscosity coefficient -- 102 104 100 ISO2909 Base number mgKOH/g 39.8 39.2 40.2 SH/T 0251 Flash point ° C. 250 254 249 GB/T 261 Sulfated ash, % w % 6.53 6.39 6.31 GB/T 2433 PDSC min 12.74 13.34 11.96 SH/T 0719, the test condition is: 200° C., 3.0 MPa, O₂ Pb value by four-ball N 1117 1117 1186 GB/T 3142 test Long wear extent by mm 0.34 0.35 0.34 SH/T 0189 four-ball test Coking test mg 21 24 18 SH/T 0300 Gel test ml 0.4 0.25 0.5 1% of water and 99% of oil are blended in the test tube, stirred by an agitator blade (2000 rpm) for 60 sec and stored at 70° C. for 96 h. The precipitation amount at tube bottom is observed.

[0042] The composite additive designed for the BOB system using double detergents provided by the present invention can be blended with system oils so as to provide cylinder oils that can satisfy the requirement of the engine. Such composite additive has been tested by sailing over 4000 hours wherein BP Energol OE-HT30 is used as the system oil by the vessel, and has been technically certified by MAN B&W. Samples of the fresh/waste cylinder oils using such composite additive during the sailing were monitored, and the data are illustrated in FIG. 2.

[0043] Throughout the test of 4000 hours, the base number of the cylinder oil formulated from the composite additive decreased from 70 mgKOH/g at the beginning, through 60 mgKOH/g and 50 mgKOH/g, to 40 mgKOH/g at the end. The entire sailing test could be divided into four stages according to the base number of the cylinder oil, and each stage lasted about 1000 hours. It can be clearly seen from FIG. 2 that the residual base number in the waste oil was not notably decreased, and the Fe content resulted from the wear was not notably increased, either, that is, the both important index fluctuated within normal ranges.

[0044] 1. The Fe content in the waste oil was never abnormally high, and the Fe content of all the samples was always less than 200 ppm, which satisfied the requirement of the engine OEM about the performance of cylinder oils;

[0045] 2. The residue base number of the waste oil from the four different stages tended to decrease due to the decrease of the base number of fresh oils. Furthermore, even if the cylinder oil with a base number of 40 mgKOH/g was used, the residue base number in the waste oil was still above 12 mgKOH/g. It is shown that the composite additive has strong ability to "store" the base number, and thus effectively prevent the wear of engine parts to occur.

[0046] In conclusion, the cylinder lubricating oil maintained steady combination performance in case that the variation of the dosage of the composite additive reached the extent close to 50%, especially in terms of the antiwear performance under extreme pressure and the ability to preserve the base number. The test results sufficiently satisfied the requirement of the engine about the lubricating oil performance and were technically certified by the engine OEM.

Claims

1. (canceled)

2. An engine system, comprising: a system oil storage tank having a system oil outlet stream for providing a system oil; an additive tank having an additive outlet stream for providing a composite additive comprising 25-45% sulfonate detergent with superhigh base number, 40-60% phenolate detergent with low base number, 0-8% dispersing agent, 0-4% antiwear agent, and 10-20% Group I base oil with high viscosity index which is selected from the group consisting of 400SN, 500SN and 600SN; a blend on board device operably connected to the system oil outlet stream and the composite additive outlet stream and having a cylinder oil outlet stream, the blend on board device being operable to combine the system oil with the composite additive to form a cylinder oil having a predetermined base number; a cylinder oil storage tank operably having an ejector outlet stream, the cylinder oil storage tank connected to the cylinder oil outlet stream and configured to retain receive the cylinder oil for a predetermined period of time; and a main engine operably connected to a fuel oil inlet stream and the ejector outlet stream to receive the retained cylinder oil and intermix the fuel oil with the cylinder oil.

3. The engine system of claim 2, wherein: the sulfonate detergent with superhigh base number is C₂₂-C₃0 linear alkyl benzene calcium sulphonate, wherein the base number thereof is 395-430 mgKOH/g; the phenolate detergent with low base number is C₂₀-C₂5 alkyl sulfurized calcium phenolate, wherein the base number thereof is 240-265 mgKOH/g; the dispersing agent is selected from the group consisting of mono-polyisobutylene succinimide, bis-polyisobutylene succinimide and multi-polyisobutylene succinimide; the antiwear agent is zinc long-chain alkyl thiophosphate with the structure corresponding to the following formula, ##STR00002## wherein R₁, R₂, R₃ and R₄ are long-chain primary alkyl groups each comprising 12-18 carbon atoms, or R₁, R₂, R₃ and R₄ are long-chain secondary alkyl groups each comprising 12-16 carbon atoms.

4. The engine system of claim 2, wherein the kinematic viscosity of said base oil is 8.5-11.5 cSt at 100.degree. C.

5. The engine system of claim 2, wherein the cylinder oil resulting from the combination of the system oil with the composite additive has a base number greater than or equal to 285 mgKOH/g.

6. The engine system of claim 2, wherein the cylinder oil resulting from the combination of the system oil with the composite additive has a kinematic viscosity at 100.degree. C. less than or equal to 95 mm²/s.

7. A method for treating a marine cylinder oil comprising: blending a marine cylinder oil, in a shipborne Blender-on-Board system; with a composite additive comprising, based on the total weight of the composite additive: 25-45% sulfonate detergent with superhigh base number, 40-60% phenolate detergent with low base number, 0-8% dispersing agent, 0-4% antiwear agent, and 10-20% Group I base oil with high viscosity index which is selected from the group consisting of 400SN, 500SN and 600SN; wherein: the sulfonate detergent with superhigh base number is C₂₂-C₃0 linear alkyl benzene calcium sulphonate, wherein the base number thereof is 395-430 mgKOH/g; the phenolate detergent with low base number is C₂₀-C₂5 alkyl sulfurized calcium phenolate, wherein the base number thereof is 240-265 mgKOH/g; the dispersing agent is selected from the group consisting of mono-polyisobutylene succinimide, bis-polyisobutylene succinimide and multi-polyisobutylene succinimide; the antiwear agent is zinc long-chain alkyl thiophosphate with the structure corresponding to the following formula, ##STR00003## wherein R₁, R₂, R₃ and R₄ are long-chain primary alkyl groups each comprising 12-18 carbon atoms, or R₁, R₂, R₃ and R₄ are long-chain secondary alkyl groups each comprising 12-16 carbon atoms.

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