USE OF SPECIFIC BASE OIL FOR REDUCING PARTICULATE EMISSIONS

Description

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a U.S. National Phase Application under 35 U.S.C. § 371 of International Patent Application No. PCT/EP2023/062442 filed May 10, 2023, which claims priority of French Patent Application No. 22 10488, filed Oct. 12, 2022 and French Patent Application No. FR 22 04459, filed May 11, 2022. The entire contents of which are hereby incorporated by reference.

FIELD OF THE INVENTION

The present invention relates to the use of a specific base for reducing particle emissions from motor vehicles.

BACKGROUND

In 1993, the first European standard on emissions from vehicles with combustion engines was introduced. The standard Euro VI anti-pollution (standard EC 595/2009) relating to heavy goods vehicle engines came into force on 1 Sep. 2014 for newly approved vehicles and applicable to all new vehicles as of 1 Jan. 2014. The above standard concerns four pollutants in particular: carbon monoxide (CO), unburned hydrocarbons (HC), nitrogen oxides (NOx), particle mass (PM) and number (PN), amongst which soot, the last two remaining the most problematic for the pollution control system of modern engines.

Going after CO₂ prompted manufacturers to increase the efficiency thereof so as to lower the consumptions. To this end, a for lean-burn operation (air in excess compared to the mass of fuel) was often chosen. Unfortunately, such a process generates a significant increase in the emissions of nitrogen oxide and particles.

In the past, manufacturers have also chosen to introduce particle filter systems for reducing the number and mass of particles emitted into the atmosphere. In most cases, the operation of such systems is based on the combustion of soot due to the temperature rise of the exhaust gases at the inlet of the filter. Such operation requires the presence of catalysis.

To comply with current and future standards, strict regulations on particle size and more particularly on the concentration in number of particles emitted (PN) have been introduced. Several studies have shown that, although particulate mass formation is low, the PN of particulates emitted by compressed natural gas (CNG) engines are not negligible compared to same of diesel engines, especially under high engine load conditions.

For the above reason, the new Euro VI emission standards prescribe a limit of 6×10¹¹ particles per kWh, for diesel and CNG heavy vehicles.

The use of lubricant composition is considered to make a significant contribution to the emission of small particles (greater than 10 nm or 23 nm) emitted by the above type of engine.

There is an interest in providing lubricating compositions specifically suitable for reducing the number of particles emitted at the exhaust of a vehicle, in particular of a vehicle comprising at least one controlled ignition engine, preferably a combustion engine, in particular heavy or light vehicles, e.g. vehicles such as heavy goods vehicles.

SUMMARY

A goal of the present invention is to provide a suitable lubricating composition having a direct impact on particle emissions.

Another goal of the present invention is to provide a specific base oil making the lubricating composition have a direct impact on particle emissions.

Further goals will emerge upon reading the following description of the invention.

DETAILED DESCRIPTION

Such goals are fulfilled by the present application which relates to the use of a lubricating composition comprising a base oil or a mixture of base oils having a viscosity (BOV or Base Oil Viscosity) of less than or equal to 4.5 mm²/s, in particular less than or equal to 4 mm²/s, for reducing the particulate emissions from an engine.

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 said base oil or said mixture of base oils has a kinematic viscosity (BOV or base oil viscosity) measured at 100° C., as per the standard ASTM D445, of less than or equal to 4.5 mm²/s, and wherein the lubricating composition has a viscosity at 150° C. and under constant shear of greater than or equal to 2.4 mPa.s⁻¹.

In the context of the present invention, the term “particles” refers to the particles emitted by the exhaust of motor vehicles. It means a group of microscopic particles (about μm or less in size). Such substances are varied and are comprised in the vehicle exhaust gases coming from the combustion of fuel. Such substances can be either solid or liquid. The term particles comprises the term soots, which are formed, are oxidized and contain unburned hydrocarbons, oxygenated derivatives (ketones, esters, aldehydes, lactones, ethers, organic acids) and polycyclic aromatic hydrocarbons (the famous PAHs) along with the nitrated, oxygenated derivatives thereof, etc. There are further mineral (SO2, sulphates, etc.) and metal derivatives.

In a particularly advantageous manner, the present invention can be used for reducing the emissions of particles with a size greater than or equal to 10 nm, e.g. greater than 23 nm, or in particular equal to 10 nm.

Within the framework of the present invention, the term “particle size” refers to particles, or agglomerate of particles the size of which is comprised between 10 and 100 nm, e.g. between 10 and 60 nm, and else preferably 10 to 40 nm, e.g. between 23 and 100 nm, preferably between 23 and 60 nm, and else preferably between 23 and 40 nm.

The particle size can be measured by spectrometry, e.g. using a spectrometer manufactured by Cambustion under the commercial reference DMS500. The number of particles according to the size (PN10 or PN23) thereof can be determined e.g. using particle counters such as APC 489 marketed by AVL or else MEXA-2000 SPCS marketed by HORIBA.

Reduction of particle emissions refers, in particular, to the reduction of the number of particles, in particular of particles having a size greater than or equal to 10 nm, e.g. greater or equal to 23 nm. It is in particular a question of reducing the number of particles emitted during a cycle on a WHTC regulatory cycle, e.g. during WLTC or RDE cycles. Thereof is measured according to the work supplied over the cycle (in #/kWh). The reduction is also measured as a function of the number of kilometers traveled.

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

Preferably, the present invention relates to the reduction of emissions of particles, preferably of particles with a size greater than or equal to 10 nm, e.g. greater than or equal to 23 nm, preferably of soots, over the entire regulatory cycle for heavy goods vehicle WHTC (World Harmonized Transient Cycle) applications.

Preferably, the present invention relates to the reduction of the emission of particles, preferably particles of size less than or equal to 23 nm, preferably soots, during the urban (low speed), peri-urban (moderate speed) and road (high speed) cycles defined by the WLTC (or WLTP) (Worldwide Harmonized Light Vehicle Test Procedure) and across all WLTC, and also over the RDE (Real Drive Emissions) cycle.

In the context of the present invention, viscosity (also called BOV for Base Oil Viscosity) is a kinematic viscosity and is measured at 100° C., according to the standard ASTM D445. The viscosity of the base oil at 100° C. corresponds to the kinematic viscosity of the base oil mixture at 100° C. of the formulation before the addition viscosity modifier additives and of a pour point depressor.

In the case of a base oil mixture, it should be understood that the viscosity of the base oil mixture is less than or equal to 4.

Preferably, the base oil or base oil mixture has a viscosity comprised between 1.5 and 4.

In the case of a mixture of base oils, it should be understood that it is the viscosity of the mixture of base oils which is preferably less than or equal to 4.5 mm²/s.

Preferably, the base oil or the mixture of base oils has a kinematic viscosity, measured at 100° C., of from 1.5 to 4.5 mm²/s, in particular from 1.5 to 4 mm²/s.

According to one embodiment, the kinematic viscosity, measured at 100° C., of the base oil or of the mixture of base oils is comprised between 3 and 4.5 mm²/s, and preferentially between 4 and 4.5 mm²/s.

Preferably, the viscosity index of the base oil or of the mixture of base oils is greater than or equal to 130, preferably greater than or equal to 150.

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

The lubricating composition according to the invention has e.g. a grade according to the SAEJ300 classification of type XW-(Y) with X representing 0, 5 or 10 and Y representing an integer comprised between 6 and 50, or comprised between 8 and 40, preferably 12 or 30 or 40.

The base oils used in the lubricating compositions of the invention can be oils of mineral or synthetic origin belonging to groups I to V according to the classes defined by the API classification (or the equivalents thereof according to the ATIEL classification (Table 1) or the mixtures thereof.

	TABLE 1
	Concentration of	Sulfur	Viscosity
	saturated	concen-	index
	substances	tration	(VI)

Group I	<90%	>0.03%	80 ≤ VI < 120
Mineral oils
Group II	≥90%	≤0.03%	80 ≤ VI < 120
Hydrocracked oils
Group III	≥90%	≤0.03%	≥120
Hydro-isomerized oils

Group IV	Polyalphaolefins (PAO)
Group V	Esters and other bases not
	included in groups I to IV

The mineral base oils of the invention include any type of base oil obtained by atmospheric distillation and vacuum distillation of crude oil, followed by refining operations such as solvent extraction, deasphalting, solvent dewaxing, hydrotreatment, hydrocracking, hydroisomerization and hydrofinishing.

The base oils of the lubricating compositions used according to the invention can be further chosen from synthetic oils, such as certain esters of carboxylic acids and alcohols, and polyalphaolefins. The polyalphaolefins used as base oil are e.g. obtained from monomers comprising from 4 to 32 carbon atoms, e.g. from octene or decene, and for which the viscosity at 100° C. is comprised between 1.5 and 15 mm².s⁻¹ as per the standard ASTM D445.

The lubricating composition used according to the invention can comprise at least 50% by weight of base oil with respect to the total weight of the composition. More advantageously, the lubricating composition according to the invention comprises at least 60% by weight, or even at least 70% by weight of base oils with respect to the total weight of the lubricating composition. In a more preferred way, the lubricating composition according to the invention comprises from 50% to 97% by weight of base oils, preferably from 50% to 85% by weight of base oils, or from 75% to 97% by weight of base oils with respect to the total weight of the composition.

According to one embodiment, the quantity of base oil or of the mixture of base oils is between 50% and 97% by weight with respect to the total weight of the lubricating composition as defined hereinabove.

As mentioned hereinabove, the lubricating composition used according to the invention preferably has a viscosity at 150° C. and under constant shear greater than or equal to 2.4 mPa.s⁻¹. The viscosity is also referred to by the term HTHS 150.

HTHS (High Temperature, High Shear) viscosity is a measure of the viscosity of the residual oil film under high stress (shear under mechanical pressure) at high temperature. Herein, the HTHS 150 viscosity value is measured at 150° C. The values are measured as per the standards CEC L-036-90 or ASTM D4683.

According to one embodiment, the viscosity at 150° C., and under constant shear, of the lubricating composition (or HTHS 150) is comprised between 2.4 mPa.s⁻¹ and 5 mPa.s⁻¹, preferably between 2.6 mPa.s⁻¹ and 5 mPa.s⁻¹.

According to one embodiment, the lubricating composition used according to the invention has a grade according to the SAEJ300 classification of type XW-(Y) with X representing 0, 5 or 10 and Y representing an integer comprised from 6 to 50, preferably from 8 to 40, preferably 12, 20, 30 or 40, preferentially 20 or 30.

The lubricating composition used according to the invention may also comprise at least one viscosity index improving additive such as a butylene and hydrogenated styrene polymer, an ethylene propylene copolymer, or else a polymethacrylate polymer, preferably a butylene and hydrogenated styrene polymer. The lubricating composition according to the invention may thus also comprise at least one additive improving the viscosity index, chosen from the group consisting of hydrogenated butylene and styrene polymers, ethylene propylene copolymers and polymethacrylate polymers, said viscosity index improving additive preferably being a hydrogenated butylene and styrene polymer. The lubricating composition according to the invention can comprise from 0.1% to 15% by weight of additive improving the viscosity index, with respect to the total weight of lubricating composition.

The composition of the invention can further comprise at least one additive.

Many additives can be used in the lubricating compositions according to the invention.

The preferred additives for the lubricating composition according to the invention are chosen from detergent additives, friction modifying additives different from the molybdenum compounds defined above, extreme pressure additives, dispersants, pour point activators, antifoaming agents, thickeners and mixtures thereof.

Preferentially, the lubricating compositions according to the invention comprise at least one extreme pressure additive, or a mixture.

Anti-wear additives and extreme pressure additives protect surface friction by forming a protective film adsorbed on the surfaces.

There is a wide variety of anti-wear additives. Preferentially, for the lubricating compositions of the invention, the anti-wear additives are chosen from additives comprising phosphorus and sulfur, such as alkylthiophosphate metals, in particular zinc alkylthiophosphate, and more precisely zinc dialkyldithiophosphate or ZnDTP. Preferred compounds have the formula Zn((SP(S)(OR)(OR′))2, wherein R and R′—either identical or different—independently stands for an alkyl group, preferentially an alkyl group comprising from 1 to 18 carbon atoms.

Amine phosphates as well are anti-wear additives which can be used in the lubricating compositions of the invention. However, the phosphorus atoms provided by such additives can act as a poison in the catalytic systems of automobiles since same generate ash. Such effects can be minimized by substituting part of the amine phosphates with non-phosphorus additives, such as polysulfides, in particular sulfur-containing olefins.

Advantageously, the lubricating compositions according to the invention can comprise from 0.01% to 6% by weight, preferentially from 0.05% to 4% by weight, more preferentially from 0.1% to 2% by weight with respect to the total weight of lubricating composition of anti-wear additives and extreme pressure additives.

Advantageously, the lubricating compositions according to the invention comprise from 0.01% to 6% by weight, preferentially from 0.05% to 4% by weight, more preferentially from 0.1% to 2% by weight with respect to the total weight of lubricating composition, of anti-wear additives (or anti-wear compounds).

Advantageously, the compositions according to the invention can comprise at least one friction modifying additive different from the molybdenum compounds of the invention. The friction modifying additives can in particular be chosen from compounds providing metallic elements and ashless compounds. Compounds providing metal elements include complexes of transition metals such as Mo, Sb, Sn, Fe, Cu, Zn for which the ligands can be hydrocarbon compounds comprising oxygen, nitrogen, sulfur or phosphorus atoms. Ashless friction modifying additives are generally of organic origin or can be chosen from fatty acid and polyol monoesters, alkoxylated amines, alkoxylated fatty amines, fatty epoxides, fatty epoxide borates, fatty amines or glycerol acid esters. According to the invention, fatty compounds comprise at least one hydrocarbon group comprising from 10 to 24 carbon atoms.

Advantageously, the lubricating composition according to the invention can comprise from 0.01% to 2% by weight or from 0.01% to 5% by weight, preferentially from 0.1% to 1.5% by weight or from 0.1% to 2% by weight with respect to the total weight of lubricating composition, of a friction modifier additive different from the molybdenum compounds according to the invention.

Advantageously, the lubricating composition according to the invention can comprise at least one antioxidant additive.

Antioxidant additives generally delay the degradation of the lubricating composition. Such degradation is most often expressed by a deposit formation, by the presence of sludge or by an increase in the viscosity of the lubricating composition.

Antioxidant additives generally act as radical inhibitors or hydroperoxide destructor inhibitors. Commonly used antioxidants include phenolic antioxidants, amine antioxidants, antioxidants containing sulfur and phosphorus. Some of the antioxidants, e.g. antioxidants containing sulfur and phosphorus, can generate ash. The phenolic antioxidant additives can be ashless or in the form of neutral or basic metal salts. The antioxidant additives can in particular be chosen from sterically hindered phenols, sterically hindered phenol esters, sterically hindered phenols comprising a thioether bridge, diphenylamines, diphenylamines substituted with at least one C1 to C12 alkyl group, N,N′-dialkyl-aryl-diamines and mixtures thereof.

Preferentially, according to the invention, the sterically hindered phenols are chosen from compounds comprising a phenol group for which at least one of the carbon atoms in the vicinity of the carbon atom bearing the alcohol function is substituted by at least one C1 to C10 alkyl group, preferentially a C1 to C6 alkyl group, preferentially a C4 alkyl group, preferentially a tert-butyl group.

Amine compounds are another class of antioxidant additives which can be used, optionally in combination with phenolic antioxidant additives. Examples of amine compounds are aromatic amines, e.g. aromatic amines with the formula NRaRbRc wherein Ra stands for an aliphatic group or an optionally substituted aromatic group, Rb stands for an optionally substituted aromatic group, Rc stands for a hydrogen atom, an alkyl group, an aryl group or group with the formula RdS(O)zRe wherein Rd stands for an alkylene or alkenylene group, Re stands for an alkyl group, an alkenyl group or an aryl group, and z stands for 0, 1 or 2.

Alkyl phenols containing sulfur or the alkali or alkaline-earth metal salts thereof can further be used as antioxidant additives.

Other classes of antioxidant additives are compounds comprising copper, e.g. copper thio-or dithio-phosphate, copper salts and carboxylic acids, dithiocarbamates, sulfonates, phenates, copper acetylacetonates. Copper salts I and II, succinic acid salts or succinic anhydride salts can be further used.

The lubricating compositions used according to the invention can further comprise any type of antioxidant known to a person skilled in the art.

Advantageously, the lubricating composition used comprises at least one ashless antioxidant additive.

Further advantageously, the lubricating composition used according to the invention comprises from 0.1% to 2% by weight with respect to the total weight of the composition, of at least one antioxidant additive.

The lubricating composition used according to the invention can further comprise at least one detergent additive.

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

The detergent additives which can be used in the lubricating compositions according to the invention are generally known to a person skilled in the art. The detergent additives can be anionic compounds comprising a long lipophilic hydrocarbon chain and a hydrophobic head. The associated cation can be a metal cation of an alkali or alkaline earth metal.

The detergent additives are preferentially chosen from alkali metal or alkaline-earth metal salts of carboxylic acid, sulphonates, salicylates, naphthenates, as well as phenate salts. The alkali metals and alkaline earth metals are preferentially calcium, magnesium, sodium or barium.

Such metal salts generally include the metal in a stoichiometric or in an excess amount, i.e. in a concentration greater than the stoichiometric concentration. Same are then overbased detergents; the excess of metal involving the overbased nature of the detergent additive is generally in the form of an oil-insoluble metal salt, e.g. carbonate, hydroxide, oxalate, acetate, glutamate, preferentially carbonate.

Advantageously, the lubricating composition used according to the invention can comprise from 0.5% to 8% or from 2% to 4% by weight with respect to the total weight of the lubricating composition, of an overbased detergent additive.

Further advantageously, the lubricating composition used according to the invention can further comprise an additive which lowers the pour point.

By slowing down the formation of paraffin crystals, the pour point lowering additive generally improves the behavior under cold conditions of the lubricating composition, according to the invention.

Examples of additives lowering the pour point include alkyl polymethacrylates, polyacrylates, polyarylamides, polyalkylphenols, polyalkylnaphthalene, alkyls polystyrenes.

Advantageously, the lubricating composition according to the invention can further comprise a dispersing agent.

The dispersing agents can be chosen from Mannich bases, succinimides and derivatives thereof.

Further advantageously, the lubricating composition according to the invention can comprise from 0.2% to 10% by weight with respect to the total weight of lubricating composition, of dispersing agent.

The lubricating composition according to the invention can further comprise at least one thickening agent.

The lubricating composition according to the invention can further comprise an antifoaming agent and a demulsifying agent.

The present invention further relates to the use of base oil with a viscosity less than or equal to 4 in an engine lubricating composition, so as to reduce particle emissions of said engine.

The present invention further relates to the use as defined hereinabove, wherein the reduction of particle emissions relates to the WLTC cycle or the RDE cycle, and more particularly to the reduction of emissions of particles with a size greater than or equal to 10 nm, e.g. comprised between 10 nm and 40 nm.

The present invention further relates to a method for reducing the emission of particles in an engine, preferentially a gas, gasoline, diesel or further hybrid engine, comprising the use of a lubricating composition comprising a base oil with a viscosity less than or equal to 4.

The present invention also relates to a method for reducing the emission of particles in an engine, in particular a controlled ignition engine, e.g. a 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, wherein said base oil or said mixture of base oils has a kinematic viscosity (BOV or base oil viscosity) measured at 100° C., as per the standard ASTM D445, less than or equal to 4.5 mm²/s, and wherein said lubricating composition has a viscosity at 150° C. and under constant shear greater than or equal to 2.4 mPa.s⁻¹.

The present invention further relates to a method for reducing the emission of particles in an engine, preferably a gas, gasoline, diesel or hybrid engine, lubricated by a lubricating composition comprising the addition of a base oil with a viscosity less than or equal to 4, to said lubricating composition.

The present invention further relates to a method for reducing the emission of particles in an engine, preferably a gas, gasoline, diesel or hybrid engine, lubricated by a lubricating composition comprising a base oil or a mixture of base oils, wherein said base oil or said mixture of base oils has a kinematic viscosity (BOV or base oil viscosity) measured at 100° C., as per the standard ASTM D445, less than or equal to 4.5 mm²/s, and wherein said lubricating composition has a viscosity, at 150° C. and under constant shear, greater than or equal to 2.4 mPa.s⁻¹.

In such methods, the particles, the base oil and the lubricating composition are as defined hereinabove.

The present invention covers all motor vehicles, in particular vehicles comprising a 2-stroke or 4-stroke engine, gasoline, diesel, hybrid or gas engines.

The present invention covers all motor vehicles, preferably comprising at least one controlled ignition engine, preferably a combustion engine, in particular heavy vehicles or light vehicles, preferably heavy goods vehicles.

The present invention will now be described with the help of non-limiting examples.

EXAMPLE 1

Lubricating Compositions

The following lubricating compositions were prepared according to Table 2 below.

	TABLE 2
			Composition 2	Composition 3	Composition 4	Composition 5
	Reference	Composition 1	(according to	(according to	(according to	(according to
	composition	(comparative)	the invention)	the invention)	the invention)	the invention)
	((in % with	(in % with	(in % with	(in % with	(in % with	(in % with
	respect to	respect to	respect to	respect to	respect to	respect to
	the total	the total	the total	the total	the total	the total
	weight of the	weight of the	weight of the	weight of the	weight of the	weight of the
	composition)	composition)	composition)	composition)	composition)	composition)

Grade	10W-40	10W-40	5W-30	5W-30	0W-40	0W-30
Additive	21.4	11.3	21.4	11.3	21.4	21.4
package
Mineral base	76.1	84.5	76	82.8	68.8	73.1
oil (group III)						(mixture of
						two base
						oils)
Base oil	6	8	4	4	3	2.9
viscosity
Hydrogenated	2.5	4.2	2.6	5.9	9.8	5.5
styrene
butadiene
polymer

The characteristics of the lubricating compositions are collated in Table 3 below:

	TABLE 3
			Composition 2	Composition 3	Composition 4	Composition 5
	Reference	Composition 1	(according to	(according to	(according to	(according to
	composition	(comparative)	the invention)	the invention)	the invention)	the invention)

KV 40° C.	91.57	94.32	56.76	52.45	74.22	50.3
ASTM
D445-97
or ISO3104
(mm2/s)
KV 100° C.	13.49	13.8	9.747	9.751	13.53	9.674
ASTM
D445-97
or ISO 3104
(mm2/s)
VI	147	149	158	174	188	181
(ISO 3104)
HTHS 150° C.	4	3.86	3.14	2.99	3.83	3.85
CEC L14-90
(mPa · s)
Noack 1 h	6.5	4.6	12.2	13.6	31.5	32
250° C.
CEC L-040-93
(%)

EXAMPLE 2

Measurement of the Number of Emitted Particles and of Fuel Eco

The compositions of example 1 were tested over the WHTC cycle and the quantity of particles having a size greater than or equal to 10 nm emitted at the end of each cycle was measured.

The engine tests were carried out on turbocharged straight-six engines. The tests were carried out at the same starting temperature of the engine. All other test bench conditions were kept constant as well. Sampling for the exhaust gas measurements was carried out from raw exhaust gases ahead from the exhaust system but after the treatment systems. Thereby, the effects observed are indeed due solely to the use of the lubricating composition and not to any other criterion such as the temperature, the humidity, etc.

The particle size distribution was measured in parallel by a Cambustion differential mobility spectrometer (DMS500). Same uses a high voltage discharge for charging every particle proportionally to the surface thereof. The charged particles are introduced into a classification section with a strong radial electric field. Such field causes particles to drift through a flow inside a column, toward the electrometer detectors. The particles are detected at different distances in the column, depending on the aerodynamic resistance/Icharge ratio thereof. The outputs of the 22 electrometers are processed in real-time at 10 Hz, so as to provide spectral data and other measurements.

Fuel consumption was also measured and calculated by the following equation:

Fuel ⁢ consumption = Total ⁢ mass ⁢ of ⁢ fuel ⁢ injected [ g ] cycle [ kWh ]

The emissions of particles were calculated as follows:

Emissions ⁢ of ⁢ particles = Total ⁢ number ⁢ of ⁢ particles [ # ] cycle [ kWh ]

The results are given in Table 4 hereinbelow:

	TABLE 4
			Composition 2	Composition 3	Composition 4	Composition 5
	Reference	Composition 1	(according to	(according to	(according to	(according to
	composition	(comparative)	the invention)	the invention)	the invention)	the invention)

Fuel	248	249	246	249	249	245
consumption
(g/kWh)
Emissions of	5.75 × 1012	3.78 × 1012	2.52 × 1012	2.18 × 1012	1.72 × 1012	1.56 × 1012
particles
(number/kWh)

The results clearly show that the choice of the base oil according to the invention (viscosity less than or equal to 4) clearly reduces particle emission. The results also show that the choice of the base oil according to the invention has no impact on the consumption of fuel (Fuel Eco), thereby showing that a reduction in particle emissions is not synonymous with an improvement of Fuel Eco.

EXAMPLE 3

1^st Testing Campaign

Preparation of Lubricating Compositions The lubricating compositions were prepared according to Table 5 hereinafter.

TABLE 5
	Composition 6	Composition 7	Composition 8	Composition 9	Composition 10
	(comparative)	(comparative)	(reference oil)	(invention)	(invention)
Grade	0W12	0W20	0W20	0W20	0W20
Package of	14	14	14	14	14
additives
Base oil	BOV 4	Mixture of	BOV 4	Mixture of 90%	Mixture of
	Group III	group III base	Group III	BOV 4 Group III	group III base
	Base oil	oils: 43% BOV	Base oil	base oil and	oils: 70% BOV
		4 oil and 57%		10% BOV 6	4 oil and 30%
		BOV 6		Group IV	BOV 3
				base oil
PISH	0.4	0	4	4.4	5.6
polymer
PMA	0	0	0	0	0
polymer

	Composition 11	Composition 12	Composition 13	Composition 14
	(invention)	(invention)	(invention)	(invention)
Grade	0W20	XW30	XW30	XW30
Package of	14	14	14	14
additives
Base oil	BOV 3	BOV 3	BOV 4	BOV 4
	Group III	Group III	Group III	Group III
	Base oil	Base oil	Base oil	Base oil
PISH	7	12.5	10.2	0
polymer
PAMA	0	0	0	10.0
polymer

The numbers in Table 5 correspond to percentages by weight with respect to the total weight of composition.

The characteristics of the lubricating compositions are given in Table 6 below:

TABLE 6
	Compo. 6	Compo. 7	Compo. 8	Compo. 9	Compo. 10
	(comp.)	(comp.)	(reference oil)	(invention)	(invention)
HTHS 150	2.17	2.55	2.64	2.6	2.6
(mPa · s−1)
CEC L-036-90 or
ASTM D4683
Base oil viscosity	4.324	5.578	4.324	4.304	3.918
(100° C.)
ASTM D445-97
(mm2/s)
Noack volatility	10.7	7.7	11.1	10.8	15.2
ASTM D5800 or
CEC L-040-93

	Compo. 11	Compo. 12	Compo. 13
	(invention)	(invention)	(invention)
HTHS 150	3.49	3.52	3.42
(mPa · s−1)
CEC L-036-90 or
ASTM D4683
Base oil viscosity	3.320	4.324	4.324
(100° C.)
ASTM D445-97
(mm2/s)
Noack volatility	21	10.7	11.4
ASTM D5800 or CEC
L-040-93

Measurement of the Number of Emitted Particles

The compositions of example 3 were subjected to the WLTC or RDE tests and the quantity of particles per kilometer traveled having a size greater than or equal to 10 nm emitted at the end of each cycle was measured. An EB2ADTS (PSA Peugeot Citroën) engine with a displacement of 1.2 I (maximum power of 60 KW) was used.

The engine tests were carried out on turbocharged straight-three engines. The tests were carried out at the same starting temperature of the engine (20° C.). All other test bench conditions were kept constant as well. Sampling for the exhaust gas measurements was carried out from raw exhaust gases at the outlet of the turbocharger and upstream of the post-treatment system.

The particle number was measured using a Horiba MEXA2000-SPCS particle counter equipped with an overhead diluter. Each lubricating composition was tested 10 times on a WLTC cycle (with forced cooling at 20° C. at the beginning of each cycle). The first 3 cycles were deliberately discarded to allow the injection system to stabilize. The other 7 cycles were taken into account for the results. Particle numbers were expressed as average particle numbers (PN10 and PN23) per kilometer over the cycle considered.

The test campaign was thus carried out on an iso-additivation matrix.

The results are given in Tables 7 and 8 hereinafter, which relate to the WLTC and RDE cycles, respectively.

The test of a reference oil (composition 8) provides a framework for each test. The test results are expressed with respect to the result of the last reference oil passed.

	TABLE 7
		Change of the number of particles
		(PN10) in comparison with the
	WLTC cycle	composition 8
	Composition 6	+23%
	(comparative)
	Composition 7	+34%
	(comparative)
	Composition 9	−8%
	(invention)
	Composition 10	−18%
	(invention)
	Composition 11	−46%
	(invention)
	Composition 12	−28%
	(invention)
	Composition 13	−26%
	(invention)

	TABLE 8
		Change of the number of particles
		(PN10) in comparison with the
	RDE cycle	composition 8
	Composition 6	+5%
	(comparative)
	Composition 7	+12%
	(comparative)
	Composition 9	−11%
	(invention)
	Composition 10	−17%
	(invention)
	Composition 11	−24%
	(invention)
	Composition 12	−4%
	(invention)
	Composition 13	−22%
	(invention)

The results of Tables 7 and 8 demonstrate that the compositions used according to the invention effectively serve to reduce the number of particles with a size greater than or equal to 10 nm, over a WLTC or RDE cycle.

Tables 9 and 10 hereinafter summarize the results obtained on an RDE or WLTC cycle for composition 8 as regards the particles with a size of 10 nm. The results show the repeatability of the effect of decreasing the emission of PN10 particles.

	TABLE 9
	Tests

	1	2	3	4	5	6	7	8

#PN10 per	2.26 ×	2.04 ×	2.23 ×	1.89 ×	1.61 ×	1.64 ×	1.84 ×	1.64 ×
km traveled	1012	1012	1012	1012	1012	1012	1012	1012
over WLTC
cycle
#PN10 per	4.88 ×	4.34 ×	4.32 ×	4.17 ×	3.57 ×	3.52 ×	3.75 ×	3.63 ×
km traveled	1012	1012	1012	1012	1012	1012	1012	1012
over RDE
cycle

	TABLE 10
	Reference oil	PN10	PN10
	Composition 8	WLTC	RDE
	Mean value	1.88E12	3.97E12
	Standard deviation	0.25E12	0.48E12
	Standard Deviation/mean	13%	12%
	Repeatability (IC95)	0.69E12	1.34E12
	Repeatability/average	37%	34%

EXAMPLE 4

2^nd Testing Campaign

A second testing campaign was carried out. Lubricants differ in viscosity grade but also in the composition of additives and of base oils. Table 11 shows the characteristics of the lubricating compositions which demonstrate an influence of the viscosity grade on the reduction of the PN10 number, independently of the composition:

TABLE 11
	Compo. 14	Compo. 15	Compo. 16	Compo. 9	Compo. 17
	(Inv.)	(inv.)	(inv.)	(inv.)	(inv.)
Grade	0W20	0W20	0W20	0W20	0W30
Package of	A (14%)	A (14%)	A (14%)	A (14%)	B (12%)
additives
Base oil	BOV 4	BOV 4	BOV 4	Mixture of	Mixture of
	Group III	Group III	Group III	90% BOV 4	40% BOV 4
	Base oil	Base oil	Base oil	Group III	Group III
				base oil and	base oil, 40% BOV
				10% BOV 6	4 Group IV
				Group IV	base oil and
				base oil	20% BOV 5
					Group III
					base oil
PISH polymer	4	4.4	4	4.4	3.2
PMA polymer					2.9
HTHS 150	2.63	2.61	2.64	2.6	3.03
(mPa · s−1)
CEC L-036-90 or
ASTM D4683
Viscosity at 100° C.	8.379	8.247	8.228	8.291	9.840
ASTM D445-97
(mm2/s)

	Compo. 18	Compo. 19	Compo. 20	Compo. 21	Compo. 22
	(inv.)	(inv.)	(inv.)	(comp.)	(comp.)
Grade	0W30	5W30	5W40	0W12	0W12
Package of	C (13%%)	D (15%)	E (13.3%)	F (13%)	F (13%)
additives
Base oil	Mixture of	Mixture of	Mixture of	Mixture of	Mixture of
	70% BOV 4	45% BOV 6	55% BOV 4	55% BOV 4	38% BOV 4
	Group III	Group III	Group III	Group III	Group III
	base oil,	base oil and	base oil and	base oil,	base oil,
	10% BOV 4	55% BOV 6	45% BOV 8	17% BOV 3	34% BOV 3
	Group IV	Group IV	Group IV	Group III	Group III
	base oil and	base oil	base oil	base oil and	base oil and
	20% BOV 5			28% BOV 3	28% BOV 3
	Group III			Group V	Group V
	base oil			base oil	base oil
PISH polymer	3.2	8.7	8.3	5	6
PMA polymer	2.7	0	0	0	0
HTHS 150	3.01	3.50	3.78	2.11	2.11
(mPa · s−1)
CEC L-036-90 or
ASTM D4683
Viscosity at 100° C.	9.890	11.28	14.54	5.978	5.967
ASTM D445-97
(mm2/s)

		Compo. 23	Compo. 24
		(comp.)	(comp.)
	Grade	0W12	0W12
	Package of additives	G (13.5%)	G (13.5%)
	Base oil	BOV 4	BOV 4
		Group III	Group III
		Base oil	Base oil
	PISH polymer	0	0
	PMA polymer	0	0
	HTHS 150	1.92	2.00
	(mPa · s−1)
	CEC L-036-90 or
	ASTM D4683
	Viscosity at 100° C.	5.457	5.868
	ASTM D445-97 (mm2/s)

Table 12 hereinafter shows the results obtained over a WLTC cycle with regard to the particles with a size of 10 nm.

	TABLE 12
	Amount of particles per
	kilometer traveled with a size
	greater than or equal to 10 nm

	Composition 14 (invention)	2.84E+12
	Composition 15 (invention)	2.49E+12
	Composition 16 (invention)	2.39E+12
	Composition 17 (invention)	2.25E+12
	Composition 10 (invention)	1.25E+12
	Composition 18 (invention)	1.14E+12
	Composition 19 (invention)	1.75E+12
	Composition 20 (invention)	5.00E+11
	Composition 21 (comparative)	3.79E+12
	Composition 22 (comparative)	4.35E+12
	Composition 23 (comparative)	4.18E+12
	Composition 24 (comparative)	4.01E+12

The results show that the use of a lubricating composition according to the invention reduces the quantity of particles with a size greater than or equal to 10 nm.