Use of Specific Base Oils for Reducing Particle Emissions

Abstract

This application relates to the use of a lubricating composition comprising a base oil or base oil mixture having a viscosity (BOV or base oil viscosity) of 4 or less for reducing particulate emissions from an engine. This application relates to the use of a lubricating composition comprising a base oil or a mixture of base oils for reducing particulate emissions from an engine, wherein the base oil or the base oil mixture has a kinematic viscosity of 4.5 mm 2 / s or less measured at 100 °C, and wherein the lubricating composition has a viscosity of 2.4 mPa·s -1 or more at 150 °C under constant shear.

Description

Technical Field

[0001] The present invention relates to the use of certain base oils for reducing particulate emissions from motor vehicles.

Background Art

[0002] The first European standards for emissions from vehicles with combustion engines were introduced in 1993. The Euro 6 emissions prevention standard (EC Regulation 595 / 2009) for engines of heavy goods vehicles came into force on 1 September 2014 for newly certified vehicles and has applied to all newly registered vehicles since 1 January 2014. The above standards relate in particular to four pollutants: carbon monoxide (CO), unburned hydrocarbons (HC), nitrogen oxides (NOx), the amount of particulate matter (PM) including soot, and the number of particles (PN), the last two being the most problematic for modern engine pollution control systems.

[0003] CO 2 By pursuing this, manufacturers have been encouraged to improve efficiency in order to reduce CO 2 consumption. For this purpose, lean burn operation (where there is an excess of air compared to the weight of the fuel) has often been selected. Unfortunately, such a process significantly increases nitrogen oxide and particulate emissions.

[0004] In the past, manufacturers have also chosen to introduce particulate filter systems to reduce the number and amount of particles emitted into the atmosphere. In most cases, the operation of such systems is based on the combustion of soot due to the increase in the temperature of the exhaust gas at the inlet of the filter. The presence of a catalytic reaction is required for such an operation.

[0005] To comply with current and future standards, strict regulations regarding particle size, and more specifically regarding the number of particles (PN) emitted, have been introduced. According to several studies, although the amount of particle formation is small, the PN of the particles emitted by compressed natural gas (CNG) engines, especially under conditions of high engine load, has been shown to be non-negligible compared to the PN emitted by diesel engines.

[0006] For the above reasons, the new Euro 6 emissions standard stipulates a limit of 6×10 11 particles per kWh for diesel and CNG heavy vehicles.

[0007] The use of lubricating compositions is thought to contribute significantly to the emission of small particles (larger than 10 nm or 23 nm) emitted by engines of the above type.

[0008] There is an advantage in providing a lubricating composition that is particularly suitable for reducing the number of particles emitted during the exhaust of vehicles, especially vehicles including at least one controlled ignition engine, preferably a combustion engine, especially heavy or light vehicles, such as heavy goods vehicles. SUMMARY OF THE INVENTION PROBLEM TO BE SOLVED BY THE INVENTION

[0009] An object of the present invention is to provide a suitable lubricating composition that has a direct effect on particle emissions.

[0010] Another object of the present invention is to provide a specific base oil such that the lubricating composition has a direct effect on particle emissions.

[0011] A further object will become apparent when reading the following description of the present invention. MEANS FOR SOLVING THE PROBLEM

[0012] This object is achieved by the present application regarding the use of a lubricating composition comprising a base oil or a mixture of base oils having a viscosity (BOV, i.e., base oil viscosity) of 4.5 mm 2 / s or less, particularly 4 mm 2 / s or less, for reducing particulate emissions from an engine.

[0013] The present invention also relates to the use of a lubricating composition comprising a base oil or a mixture of base oils for reducing particulate emissions from an engine, wherein the base oil or the mixture of base oils has a kinematic viscosity (BOV, i.e., base oil viscosity) of 4.5 mm 2 / s or less measured at 100 °C according to ASTM D445, and the lubricating composition has a viscosity of 2.4 mPa·s -1 or more at 150 °C under constant shear.

[0014] Within the scope of the present invention, the term "particles" means the particles emitted from the exhaust of a motor vehicle. It means an aggregate of fine particles (substantially of a size of μm or less). Such substances are diverse and are contained in the exhaust gas of a vehicle derived from the combustion of fuel. Such substances can be either solid or liquid. The term "particles" includes the term "soot" which is formed, oxidized, and contains unburned hydrocarbons, oxygen-containing derivatives (ketones, esters, aldehydes, lactones, ethers, organic acids) and polycyclic aromatic hydrocarbons (well-known PAHs) together with their nitrated derivatives, oxygen-containing derivatives, etc. Furthermore, inorganic substances (SO2, sulfates, etc.) and metal derivatives also exist.

[0015] Particularly advantageously, the present invention can be used for reducing particulate emissions having a size of 10 nm or more, for example 23 nm or more, or particularly equal to 10 nm.

[0016] Within the framework of the present invention, the term "particle size" means particles or aggregates of particles having a size included in the range of 10 - 100 nm, for example 10 - 60 nm, and more preferably 10 - 40 nm, for example 23 - 100 nm, preferably 23 - 60 nm, and more preferably 23 - 40 nm.

[0017] The particle size can be measured by spectroscopic analysis using a spectrometer manufactured by, for example, Cambustion under the product number DMS500. The number of particles according to the particle size (PN10 or PN23) can be measured using a particle counting device such as, for example, the APC489 commercially available from AVL or the MEXA-2000 SPCS commercially available from HORIBA.

[0018] The reduction of particulate emissions specifically means the reduction of the number of particles, particularly particles having a size of 10 nm or more, for example 23 nm or more. Reducing the number of particles emitted during the cycle in the WHTC regulation cycle, for example during the WLTC or RDE cycle, is particularly challenging. It is measured according to the work supplied over the cycle (in units of # / kWh). The reduction is also measured as a function of the number of kilometers traveled.

[0019] Preferably, the present application relates to the reduction of soot emissions.

[0020] Preferably, the present invention relates to the reduction of particles, preferably particles having a size of 10 nm or more, for example 23 nm or more, preferably soot emissions, during the application of the full regulatory cycle WHTC (World Harmonized Test Cycle) for heavy-duty vehicles.

[0021] Preferably, the present invention relates to the reduction of particles, preferably particles having a size of 23 nm or less, preferably soot emissions, during the urban (low speed), suburban (medium speed) and road (high speed) cycles defined by WLTC (or WLTP) (International Harmonized Light Vehicles Test Procedure) and over the entire WLTC, and also over the RDE (Real Driving Emissions) cycle.

[0022] Within the scope of the present invention, the viscosity (also referred to as BOV representing Base Oil Viscosity) is kinematic viscosity and is measured at 100 °C in accordance with ASTM D445 standard. The viscosity of the base oil at 100 °C corresponds to the kinematic viscosity of the base oil mixture at 100 °C in the formulation before the addition of viscosity adjusting additives and pour point depressants.

[0023] In the case of the base oil mixture, it should be understood that the viscosity of the base oil mixture is 4 or less.

[0024] Preferably, the base oil or the base oil mixture has a viscosity of 1.5 to 4.

[0025] In the case of the mixture of base oils, preferably 4.5 mm 2 / s or less should be understood as the viscosity of the mixture of base oils.

[0026] Preferably, the base oil or the mixture of base oils has a kinematic viscosity measured at 100 °C of 1.5 to 4.5 mm 2 / s, particularly 1.5 to 4 mm 2 / s.

[0027] According to one embodiment, the kinematic viscosity of the base oil or the mixture of base oils measured at 100 °C is 3 to 4.5 mm 2 / s, and preferably 4 to 4.5 mm 2 / s.

[0028] Preferably, the viscosity index of the base oil or the mixture of base oils is 130 or more, preferably 150 or more.

[0029] The viscosity index is calculated by measuring the kinematic viscosity at 40 °C and 100 °C. The measurement results are then compared with the results of two reference oils. The calculation method is described in ASTM D2270 standard.

[0030] The lubricating composition according to the present invention has, for example, a grade according to the SAE J300 classification of the XW-(Y) type, where X represents 0.5 or 10, and Y represents an integer of 6 to 50, or 8 to 40, preferably 12 or 30 or 40.

[0031] The base oil used in the lubricating composition of the present invention can be a mineral or synthetically derived oil belonging to Groups I to V (or its equivalent according to the ATIEL classification (Table 1)) or a mixture thereof, according to the grades defined by the API classification.

[0032] [Table 1]

[0033] The mineral base oil of the present invention includes all types of base oils obtained by atmospheric distillation and vacuum distillation of crude oil followed by purification operations such as solvent extraction, deasphalting, solvent dewaxing, hydrotreating, hydrocracking, hydroisomerization, and hydrofinishing.

[0034] The base oil of the lubricating composition used according to the present invention can further be selected from specific esters of carboxylic acids and alcohols and synthetic oils such as polyalphaolefins. The polyalphaolefin used as the base oil has a viscosity of 1.5 to 15 mm 2 / s at 100 °C, for example, and is obtained from monomers containing 4 to 32 carbon atoms, such as octene or decene.

[0035] The lubricating composition used according to the present invention can contain at least 50% by weight of base oil in relation to the total weight of the composition. More preferably, the lubricating composition according to the present invention contains at least 60% by weight, and further at least 70% by weight of base oil in relation to the total weight of the lubricating composition. More preferably, the lubricating composition according to the present invention contains 50 to 97% by weight of base oil, preferably 50 to 85% by weight of base oil or 75 to 97% by weight of base oil in relation to the total weight of the composition.

[0036] According to one embodiment, the amount of the base oil or the mixture of base oils is 50 to 97% by weight in relation to the total weight of the lubricating composition as defined above herein.

[0037] As described above, the lubricating composition used according to the present invention preferably has a viscosity of 2.4 mPa·s at 150°C under constant shear. -1 or higher. This viscosity is also indicated by the term HTHS 150.

[0038] The HTHS (High Temperature High Shear) viscosity is a measure of the viscosity of the remaining oil film under high stress (shear under mechanical pressure) at high temperature. Here, the HTHS 150 viscosity value is measured at 150°C. The value is measured according to the standard CEC L-036-90 or ASTM D4683.

[0039] According to one embodiment, the viscosity of the lubricating composition at 150°C under constant shear (or HTHS 150) is 2.4 mPa·s -1 to 5 mPa·s -1 , preferably 2.6 mPa·s -1 to 5 mPa·s -1 .

[0040] According to one embodiment, the lubricating composition used according to the present invention has a grade according to the SAE J300 classification of the XW-(Y) type, where X represents 0.5 or 10, and Y represents an integer from 6 to 50, preferably from 8 to 40, preferably 12, 20, 30 or 40, preferably 20 or 30.

[0041] The lubricating composition used according to the present invention may contain at least one viscosity index improver such as hydrogenated butylene and styrene polymer, ethylene propylene copolymer, or further polymethacrylate polymer, preferably hydrogenated butylene and styrene polymer. Thus, the lubricating composition according to the present invention can also contain at least one additive for improving the viscosity index selected from the group consisting of hydrogenated butylene and styrene polymer, ethylene propylene copolymer and polymethacrylate polymer, and the viscosity index improver is preferably hydrogenated butylene and styrene polymer. The lubricating composition according to the present invention can contain 0.1 to 15% by weight of the viscosity index improver in relation to the total weight of the lubricating composition.

[0042] The composition of the present invention may further contain at least one additive.

[0043] In the lubricating composition according to the present invention, many additives can be used.

[0044] Preferred additives for the lubricating composition according to the present invention are selected from detergent additives, friction modifier additives different from the molybdenum compounds defined above, extreme pressure additives, dispersants, pour point depressants, defoamers, thickeners and mixtures thereof.

[0045] Preferably, the lubricating composition according to the present invention contains at least one extreme pressure additive or mixture.

[0046] Antiwear additives and extreme pressure additives protect the surface friction by forming a protective film adsorbed on the surface.

[0047] There are a wide variety of antiwear additives. Preferably, for the lubricating composition of the present invention, the antiwear additive is selected from additives containing phosphorus and sulfur, such as metal alkylthiophosphates, specifically zinc alkylthiophosphates, and more precisely zinc dialkyldithiophosphates, i.e., ZnDTP. Preferred compounds have the formula Zn((SP(S)(OR)(OR’))2, where R and R’, which may be the same or different, independently represent an alkyl group, preferably an alkyl group containing 1 to 18 carbon atoms.

[0048] Amine phosphates are also antiwear additives that can be used in the lubricating composition of the present invention. However, the phosphorus atoms provided by such additives generate ash and can act as poisons in the automotive catalyst system. Such effects can be minimized by substituting a part of the amine phosphate with non-phosphorus additives such as polysulfides, specifically sulfur-containing olefins.

[0049] Advantageously, the lubricating composition according to the present invention can contain 0.01 to 6% by weight, preferably 0.05 to 4% by weight, more preferably 0.1 to 2% by weight of an antiwear additive and an extreme pressure additive in relation to the total weight of the lubricating composition.

[0050] Advantageously, the lubricating composition according to the present invention contains 0.01 to 6% by weight, preferably 0.05 to 4% by weight, more preferably 0.1 to 2% by weight of an antiwear additive (or antiwear compound) in relation to the total weight of the lubricating composition.

[0051] Advantageously, the composition according to the present invention can contain at least one friction modifier additive different from the molybdenum compound of the present invention. The friction modifier additive can be selected in particular from compounds providing a metal element and ashless compounds. The compounds providing a metal element include complexes of transition metals such as Mo, Sb, Sn, Fe, Cu, Zn, etc., where the ligand can be a hydrocarbon containing an oxygen, nitrogen, sulfur or phosphorus atom. Ashless friction modifier additives are generally of organic origin or can be selected from fatty acids and polyol monoesters, alkoxylated amines, alkoxylated aliphatic amines, aliphatic epoxides, aliphatic epoxide borates, aliphatic amines or glycerol esters. According to the present invention, the aliphatic compound contains at least one hydrocarbon group containing 10 to 24 carbon atoms.

[0052] Advantageously, the lubricating composition according to the present invention can contain 0.01 to 2% by weight or 0.01 to 5% by weight, preferably 0.1 to 1.5% by weight or 0.1 to 2% by weight of a friction modifier additive different from the molybdenum compound according to the present invention.

[0053] Advantageously, the lubricating composition according to the present invention can contain at least one antioxidant additive.

[0054] Antioxidant additives generally retard the deterioration of the lubricating composition. Such deterioration is most often manifested by deposit formation, the presence of sludge, or an increase in the viscosity of the lubricating composition.

[0055] Antioxidant additives generally act as radical inhibitors or hydroperoxide destructor inhibitors. Commonly used antioxidants include phenolic antioxidants, amine antioxidants, and antioxidants containing sulfur and phosphorus. Some antioxidants, such as those containing sulfur and phosphorus, can generate ash. Phenolic antioxidant additives may be ash-free or in the form of neutral or basic metal salts. Specifically, antioxidant additives can be selected from sterically hindered phenols, sterically hindered phenol esters, sterically hindered phenols containing thioether linkages, diphenylamines, diphenylamines substituted with at least one C1-C12 alkyl group, N,N'-dialkyl-aryl-diamines, and mixtures thereof.

[0056] Preferably, according to the present invention, the sterically hindered phenol is selected from compounds containing a phenol group in which at least one of the carbon atoms in the vicinity of the carbon atom carrying the alcohol functional group is substituted by at least one C1-C10 alkyl group, preferably a C1-C6 alkyl group, preferably a C4 alkyl group, preferably a tert-butyl group.

[0057] Amine compounds are another class of antioxidant additives that can optionally be used in combination with phenolic antioxidant additives. Examples of amine compounds include aromatic amines, such as aromatic amines of the chemical formula NRaRbRc, where Ra represents an aliphatic group or an optionally substituted aromatic group, Rb represents an optionally substituted aromatic group, Rc represents a hydrogen atom, an alkyl group, an aryl group, or a group of the chemical formula RdS(O)zRe, where Rd represents an alkylene or alkenylene group, Re represents an alkyl group, an alkenyl group, or an aryl group, and z represents 0, 1, or 2.

[0058] Sulfur-containing alkylphenols or their alkali metal salts or alkaline earth metal salts can also be used as antioxidant additives.

[0059] Other types of antioxidant additives are copper-containing compounds such as copper thiophosphate or copper dithiophosphate, copper salts and carboxylic acids, dithiocarbamates, sulfonates, phenates, and copper acetylacetonate. Copper salts (I) and copper salts (II), succinates or succinic anhydrides can also be used.

[0060] The lubricating composition used according to the present invention can further contain any type of antioxidant known to those skilled in the art.

[0061] Advantageously, the lubricating composition used contains at least one ashless antioxidant additive.

[0062] More advantageously, the lubricating composition used according to the present invention contains from 0.1 to 2% by weight of at least one antioxidant additive, based on the total weight of the composition.

[0063] The lubricating composition used according to the present invention can further contain at least one detergent additive.

[0064] Detergent additives generally reduce the formation of deposits on the surface of metal parts by dissolving oxidation and combustion by-products.

[0065] Detergent additives that can be used in the lubricating composition according to the present invention are generally known to those skilled in the art. The detergent additive can be an anionic compound containing a lipophilic hydrocarbon long chain and a hydrophobic head. The accompanying cation can be a metal cation of an alkali metal or an alkaline earth metal.

[0066] The detergent additive is preferably selected from alkali metal or alkaline earth metal salts of carboxylic acids, sulfonates, salicylates, naphthenates, and phenate salts. The alkali metals and alkaline earth metals are preferably calcium, magnesium, sodium, or barium.

[0067] Such metal salts generally contain metal in stoichiometric amounts or in excess, i.e., at a concentration higher than the stoichiometric concentration. At this time, these metal salts are overbased detergents, and the excess metal involved in the overbased property of the detergent additive is generally in the form of an oil-insoluble metal salt, such as carbonate, hydroxide, oxalate, acetate, glutamate, preferably in the form of carbonate.

[0068] Advantageously, the lubricating composition used according to the present invention can contain 0.5 to 8% by weight or 2 to 4% by weight of an overbased detergent additive in relation to the total weight of the lubricating composition.

[0069] Even more advantageously, the lubricating composition used according to the present invention can further contain an additive for lowering the pour point.

[0070] By retarding the formation of paraffin crystals, the pour point depressant generally improves the behavior of the lubricating composition according to the present invention under low temperature conditions.

[0071] Examples of additives for lowering the pour point include alkyl polymethacrylate, polyacrylate, polyarylamide, polyalkylphenol, polyalkylnaphthalene, and alkyl polystyrene.

[0072] Advantageously, the lubricating composition according to the present invention can further contain a dispersant.

[0073] The dispersant can be selected from Mannich bases, succinimides and their derivatives.

[0074] Even more advantageously, the lubricating composition according to the present invention can contain 0.2 to 10% by weight of a dispersant in relation to the total weight of the lubricating composition.

[0075] The lubricating composition according to the present invention can further contain at least one thickener.

[0076] The lubricating composition according to the present invention may further contain an antifoaming agent and a demulsifier.

[0077] The present invention further relates to the use of a base oil having a viscosity of 4 or less in the lubricating composition of the engine for reducing particulate emissions of the engine.

[0078] The present invention further relates to the use as defined above herein, wherein the reduction of particulate emissions is related to the WLTC cycle or the RDE cycle, and more specifically, to the reduction of particulate emissions having a size of 10 nm or more, for example, 10 to 40 nm.

[0079] The present invention further relates to a method for reducing particulate emissions in an engine, preferably a gas, gasoline, diesel or further hybrid engine, the method comprising the use of a lubricating composition containing a base oil having a viscosity of 4 or less.

[0080] The present invention also relates to a method for reducing particulate emissions in an engine, particularly a spark-ignition engine, such as a combustion engine, preferably a gas, gasoline, diesel or hybrid engine, the method comprising the use of a lubricating composition containing a base oil or a mixture of base oils, wherein the base oil or the mixture of base oils has a kinematic viscosity (BOV, i.e., base oil viscosity) of 4.5 mm 2 / s or less measured at 100 °C according to the ASTM D445 standard, and the lubricating composition has a viscosity of 2.4 mPa·s -1 or more at 150 °C and under constant shear.

[0081] The present invention further relates to a method for reducing particulate emissions in an engine, preferably a gas, gasoline, diesel or hybrid engine, lubricated by a lubricating composition, the method comprising adding a base oil having a viscosity of 4 or less to the lubricating composition.

[0082] The present invention further relates to a method for reducing particulate emissions in an engine lubricated by a lubricating composition comprising a base oil or a mixture of base oils, preferably a gas, gasoline, diesel or hybrid engine, wherein the base oil or the mixture of base oils has a kinematic viscosity (BOV, i.e., base oil viscosity) of 4.5 mm 2 / s or less measured at 100 °C according to ASTM D445 standard, and the lubricating composition has a viscosity of 2.4 mPa·s -1 or more at 150 °C under constant shear.

[0083] In such a method, the particles, base oil and lubricating composition are as defined above herein.

[0084] The present invention is directed to all motor vehicles, particularly vehicles equipped with two-stroke or four-stroke engines, gasoline engines, diesel engines, hybrid engines or gas engines.

[0085] The present invention is directed to all motor vehicles, preferably vehicles equipped with at least one controlled ignition engine, preferably a combustion engine, particularly large or small vehicles, preferably heavy goods vehicles.

Embodiments for Carrying Out the Invention

[0086] Hereinafter, the present invention will be described using non-limiting examples.

Examples

[0087] Example 1: Lubricating Composition According to Table 2 below, the following lubricating compositions were prepared.

[0088]

Table 2

[0089] The characteristics of the lubricating compositions are listed in Table 3 below.

[0090]

Table 3

[0091] Example 2: Measurement of the Number of Emitted Particles and Fuel Consumption The composition of Example 1 was tested over the WHTC cycle, and the quantity of particles having a size of 10 nm or more emitted at the end of each cycle was measured.

[0092] An engine test was carried out on an in-line six-cylinder engine with a turbocharger. The test was carried out at the same engine starting temperature. All other test bench conditions were also kept constant. Sampling for exhaust gas measurement was carried out from the raw exhaust gas in front of the exhaust system but behind the treatment system. Therefore, the observed effects are due solely to the actual use of the lubricating composition and not to any other criteria such as temperature, humidity, etc.

[0093] In parallel, the particle size distribution was measured by a Cambustion Differential Mobility Spectrometer (DMS500). For this, a high-voltage discharge is used to charge all particles in proportion to their surface area. The charged particles are introduced into a classification section with a strong radial electric field. Such an electric field drifts the particles towards the electrometer detector through the flow inside the column. The particles are detected at different distances within the column according to their aerodynamic drag / charge ratio. The outputs of 22 electrometers are processed in real time at 10 Hz to provide spectral data and other measured values.

[0094] The fuel consumption was also measured and calculated by the following equation.

[0095] Fuel consumption = Total weight of fuel injected [g] / Cycle [kWh]

[0096] The particle emissions were calculated as follows.

[0097] Particle emissions = Total number of particles [♯] / Cycle [kWh]

[0098] The results are shown in Table 4 below.

[0099]

Table 4

[0100] The results clearly show that the particulate emissions are significantly reduced by the selection of the base oil (viscosity 4 or less) according to the present invention. The results also show that the selection of the base oil according to the present invention has no effect on the fuel consumption, thus indicating that the reduction of particulate emissions is not synonymous with the improvement of fuel consumption.

[0101] Example 3: Process of Conducting the First Test [Preparation of Lubricating Composition] The lubricating composition was prepared according to Table 5 below.

[0102]

Table 5

[0103] The numbers in Table 5 correspond to weight percentages in relation to the total weight of the composition.

[0104] The properties of the lubricating composition are shown in Table 6 below.

[0105]

Table 6

[0106] Measurement of the Number of Particles Emitted The composition of Example 3 was subjected to the WLTC test or the RDE test, and the number of particles per kilometer traveled having a size of 10 nm or more emitted at the end of each cycle was measured. An EB2ADTS (PSA Peugeot Citroën) engine with a displacement of 1.2 l (maximum power 60 kW) was used.

[0107] Engine tests were carried out on an in-line three-cylinder engine with a turbocharger. The tests were carried out at the same engine starting temperature (20 °C). All other test bench conditions were also kept constant. Sampling for exhaust gas measurement was carried out from the raw exhaust gas at the outlet of the turbocharger and upstream of the aftertreatment system.

[0108] The number of particles was measured using a Horiba MEXA2000-SPCS particle counter equipped with an overhead diluter. Each lubricant composition was tested 10 times in the WLTC cycle (forced cooled to 20 °C at the start of each cycle). The first 3 cycles were intentionally excluded to stabilize the injection system. The remaining 7 cycles were considered for the results. The number of particles was expressed as the average number of particles per kilometer (PN10 and PN23) over the cycles considered.

[0109] Thus, the test implementation process was carried out with an equal additive matrix.

[0110] The results are shown in Tables 7 and 8 below, related to the WLTC cycle and the RDE cycle respectively.

[0111] The test of the reference oil (Composition 8) provides a framework for each test. The test results are presented in relation to the results of the last passing reference oil.

[0112]

Table 7

[0113]

Table 8

[0114] The results in Tables 7 and 8 show that the compositions used according to the present invention help to effectively reduce the number of particles having a size of 10 nm or more over the WLTC or RDE cycle.

[0115] The following Tables 9 and 10 summarize the results obtained in the RDE or WLTC cycles for the composition 8 with respect to particles of 10 nm size. The results show the reproducibility of the effect of reducing the emissions of PN10 particles.

[0116] [Table 9]

[0117] [Table 10]

[0118] Example 4: Process of Conducting the Second Test The second test campaign was conducted. The lubricating oils differed not only in viscosity grade but also in the composition of additives and base oils. Table 11 shows the characteristics of the lubricating compositions indicating that the viscosity grade affects the reduction of the PN10 number regardless of the composition.

[0119] [Table 11-1] [Table 11-2]

[0120] The following Table 12 shows the results obtained in the WLTC cycle for particles of size 10 nm.

[0121] [Table 12]

[0122] The results show that by using the lubricating composition according to the present invention, the quantity of particles having a size of 10 nm or more is reduced.

Claims

1. In the use of a lubricating composition comprising a base oil or a mixture of base oils for reducing particulate emissions from an engine, the base oil or the mixture of base oils has a kinematic viscosity (BOV, i.e., base oil viscosity) of 4.5 mm ２ / s or less, preferably 4 mm ２ / s or less as measured at 100 °C according to ASTM D445.

2. The base oil or mixture of base oils has a kinematic viscosity (BOV or base oil viscosity) of 4.5 mm ２ / s or less measured at 100 °C according to ASTM D445, and the lubricating composition has a viscosity of 2.4 mPa·s －１ or more at 150 °C and under constant shear. Use according to claim 1

3. Use according to claim 1 or 2, wherein the viscosity index of the base oil or the mixture of base oils is 130 or more, preferably 150 or more.

4. Use according to any one of claims 1 to 3, wherein the particles have a size of 10 nm or less, preferably equal to 10 nm.

5. The kinematic viscosity of the base oil or mixture of base oils measured at 100 °C is 1.5 to 4.5 mm ２ / s, preferably 3 to 4.5 mm ２ / s, and more preferably 4 to 4.5 mm ２ / s, and the use according to any one of claims 1 to 4.

6. The viscosity of the lubricating composition at 150 °C under constant shear is 2.4 mPa·s －１ to 5 mPa·s －１ , preferably 2.6 mPa·s －１ to 5 mPa·s －１ The use according to any one of claims 1 to 5, wherein the viscosity is as defined above.

7. Use according to any one of claims 1 to 6, wherein the lubricating composition has a grade according to the SAE J300 classification of the XW-(Y) type, where X represents 0.5 or 10 and Y represents an integer from 6 to 50, preferably 20 or 30.

8. Use according to any one of claims 1 to 7, wherein the amount of the base oil in the mixture of base oils used is 50 to 97% by weight in relation to the total weight of the lubricating composition.

9. Use according to any one of claims 1 to 8, wherein the lubricating composition further comprises at least one viscosity index improver selected from the group consisting of hydrogenated butylene and styrene polymers, ethylene propylene copolymers and polymethacrylate polymers, and the viscosity index improver is preferably a hydrogenated butylene and styrene polymer.

10. Use according to any one of claims 1 to 9, wherein the reduction of particle emissions is related to the WLTC cycle and / or the RDE cycle.

11. Use of a base oil having a viscosity of 4 mm ２ / s or less in the lubricating composition of the engine for reducing particulate emissions of the engine.

12. Use according to claim 11, wherein the base oil is as defined in any one of claims 2, 3 or 5.

13. A method for reducing particulate emissions in an engine, preferably a gas, gasoline, diesel or hybrid engine, comprising the use of a lubricating composition containing a base oil having a viscosity of 4.5 mm ２ / s or less, preferably 4 mm ２ / s or less.

14. A method for reducing particulate emissions in an engine lubricated with a lubricating composition, preferably a gas, gasoline, diesel or hybrid engine, wherein a base oil having a viscosity of 4.5 mm ２ / s or less, preferably 4 mm ２ / s or less is added to the lubricating composition.

15. A method for reducing particulate emissions in a controlled ignition internal combustion engine, preferably a gas, gasoline, diesel or hybrid engine, comprising the use of a lubricating composition comprising a base oil or a mixture of base oils, said base oil or mixture of base oils having a kinematic viscosity (BOV i.e. base oil viscosity) of 4.5 mm ２ / s or less measured at 100 °C according to ASTM D445 standard, and said lubricating composition having a viscosity of 2.4 mPa·s －１ or more at 150 °C and under constant shear.

16. Method according to claim 15, wherein the lubricating composition is as defined in any one of claims 6, 7 or 9.

17. Method according to claim 15 or 16, wherein the base oil is as defined in any one of claims 2, 3, 5 or 8.

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