Lubricating composition for preventing or reducing pre-ignition in an engine

Abstract

The present invention relates to a lubricating composition for an engine, in particular for a motor vehicle engine, comprising at least one base oil and at least one compound able to release formaldehyde under the temperature and pressure conditions of the combustion chamber of the engine. It also relates to the use, in a lubricating composition intended for an engine, of a compound able to release formaldehyde under the temperature and pressure conditions of the combustion chamber of the engine, as an additive for preventing and/or reducing pre-ignition, in particular low-speed pre-ignition (LSPI).

Claims

1. A lubricating composition for an engine, comprising: at least one synthetic base oil; and at least one formaldehyde-releasing compound configured to release formaldehyde under temperature and pressure conditions that occur in a combustion chamber of the engine, during operation of the engine, wherein the lubricating composition comprises from 0.2% to 5% by mass of the at least one formaldehyde-releasing compound, relative to the total mass of the lubricating composition, and wherein the at least one formaldehyde-releasing compound is a trioxane.

2. The lubricating composition according to claim 1, wherein the at least one formaldehyde-releasing compound is chosen from 1,3,5-trioxane, 1,2,4-trioxane, or mixtures thereof.

3. The lubricating composition according to claim 1, wherein the at least one formaldehyde-releasing compound is present in an amount ranging from 0.5% to 2% by mass, relative to the total mass of the lubricating composition.

4. The lubricating composition according to claim 1, wherein the lubricating composition comprises from 60% to 99.5% by mass of the at least one synthetic base oil, relative to the total mass of the lubricating composition.

5. The lubricating composition according to claim 1, further comprising an additional additive chosen from antioxidants, detergents, viscosity index improvers, friction modifiers, antiwear additives, extreme pressure additives, dispersants, pour point improvers, antifoams, thickeners, or mixtures thereof.

6. A method for preventing and/or reducing pre-ignition in an engine comprising: adding at least one formaldehyde-releasing compound to a lubricating composition comprising at least one synthetic base oil; and lubricating the engine using the lubricating composition, wherein the at least one formaldehyde-releasing compound is configured to release formaldehyde under temperature and pressure conditions that occur in a combustion chamber of the engine during operation of the engine, and wherein the formaldehyde reduces low-speed pre-ignition of the engine, and wherein the at least one formaldehyde-releasing compound is a trioxane.

7. The method according to claim 6, wherein the at least one formaldehyde-releasing compound is present in the lubricating composition in an amount ranging from 0.2% to 5% by mass, relative to the total mass of the lubricating composition.

8. The method according to claim 6, wherein the lubricating composition comprises: from 60% to 99.5% by mass of the at least one synthetic base oil, relative to the total mass of the lubricating composition; and an additive chosen from antioxidants, detergents, viscosity index improvers, friction modifiers, antiwear additives, extreme pressure additives, dispersants, pour point improvers, antifoams, thickeners, or mixtures thereof.

9. The method according to claim 6, wherein the lubricating the engine comprises preventing and/or reducing pre-ignition during operation of the engine.

10. A method for preventing and/or reducing pre-ignition in an engine, comprising lubricating the engine using a lubricating composition of claim 1.

11. The method as claimed in claim 10, wherein the engine is an engine that runs on gasoline, natural gas, a combination of gasoline and natural gas, diesel fuel, or a combination of natural gas and diesel fuel.

12. The method as claimed in claim 6, wherein the at least one formaldehyde-releasing compound is chosen from 1,3,5-trioxane, 1,2,4-trioxane, or mixtures thereof.

13. The method according to claim 6, wherein the lubricating the engine comprises preventing and/or reducing low-speed pre-ignition during operation of the engine.

Description

EXAMPLE

Example 1: Preparation of the Lubricating Compositions

(1) The reference composition A0, not containing any formaldehyde precursor compound, and the composition according to the invention A1, comprising a formaldehyde precursor compound required according to the invention, were prepared by mixing the various components in the amounts given in table 2 below.

(2) The proportions of the different compounds are indicated as percentages by mass.

(3) TABLE-US-00002 TABLE 2 Composition A0 A1 Base oil of group III 75 74 VI improver polymer 13 13 (styrene-butadiene) Additive package 12 12 1,3,5-trioxane —  1

Example 2: Evaluation of the Pre-Ignition-Reducing Properties of the Lubricating Compositions

(4) Evaluation Protocol

(5) The pre-ignition-reducing properties of the lubricating compositions are evaluated by evaluating the impact of each lubricating composition on low-speed pre-ignition (LSPI) For this, the LSPI phenomenon is quantified using a GM Ecotec model turbocharged spark-ignition engine composed of four inline cylinders with a total displacement of 2.0 l.

(6) After a 20-minute warm-up period at an engine speed of 2000 rpm and an engine load of 4×10.sup.5 pascals of mean effective pressure (MEP), the test procedure consists of 24 high-load sequences (18×10.sup.5 pascals MEP at a speed of 2000 rpm), called “segments”. Each segment comprises 25 000 engine cycles to ensure good statistical representation of the phenomenon studied.

(7) Each cylinder is equipped with a sensor allowing measurement of the pressure prevailing in the combustion chamber during engine operation. A high-frequency recorder records the pressure signal, allowing fine analysis of the combustion.

(8) Combustion is considered to be an LSPI event if one of the two following criteria is met: the maximum pressure of a cycle is greater than the mean of the maximum pressures over the entire sequence considered +4.7 times the standard deviation of the maximum pressure measured over the sequence; or the crankshaft angle at which 2% of the mass of the combustible mixture has burned over a given cycle is less than the mean of the crankshaft angles at which 2% of the mass of combustible mixture has burned over the entire sequence considered plus 4.7 times the standard deviation over the crankshaft angle at which 2% of the mass of combustible mixture has burned over the entire sequence.

(9) For each lubricating composition tested, the sum of the LSPI events is counted over the period of a segment, and then the mean of the LSPI events over all of the 24 segments is calculated. From this mean, an LSPI index is calculated by applying the square root of the sum of the mean of the LSPI events plus 0.5. The impact of the lubricating composition on the LSPI parameter is evaluated by comparing the LSPI index associated with this composition and taking into account the standard deviation calculated over the 24 engine segments.

(10) Result

(11) The number of LSPI phenomena was counted according to the method defined above for each of the reference composition A0 and the composition according to the invention A1. The results are given in table 3 below.

(12) TABLE-US-00003 TABLE 3 Composition A0 A1 Number of LSPI events 3.5 +/− 0.4 2.6 +/− 0.3

(13) The results show that the lubricating composition A1 according to the invention, comprising a compound able to release formaldehyde in the combustion chamber, has improved LSPT-reducing properties compared to a reference lubricating composition A0 not comprising such a formaldehyde precursor compound.