Method for reducing and/or controlling abnormal gas combustion in a marine engine or a controlled-ignition engine

1. A method for reducing and/or controlling abnormal gas combustion in an engine comprising the addition in a lubricating composition comprising at least one base oil of a copolymer (C) comprising repeat units corresponding to alkyl methacrylate monomers, said monomers comprising at least:

one or more monomer(s) (A), the same or different, selected from among (C6-C10) alkyl methacrylate monomers;

one or more monomer(s) (B), the same or different, selected from among (C10-C18) alkyl methacrylate monomers, said monomers (B) differing from said monomers (A).

2. The method according to claim 1 , wherein the copolymer (C) comprises repeat units corresponding to:

monomers (A), the same or different, selected from among (C6-C10) alkyl methacrylate monomers;

monomers (B), the same or different, selected from among (C10-C18) alkyl methacrylate monomers, said monomers (B) comprising at least one (C12) alkyl methacrylate monomer and/or at least one (C14) alkyl methacrylate monomer.

3. The method according to claim 1 , wherein monomers (A) and monomers (B) represent at least 75 weight % of the total of monomers used to prepared copolymer (C).

4. The method according to claim 1 , wherein the weight ratio of monomers (B) to monomers (A) is between about 99:1 and about 10:90.

5. The method according to claim 1 , wherein monomers (A) are branched.

6. The method according to claim 1 , wherein copolymer (C) comprises units corresponding to C10 alkyl methacrylate, C12 alkyl methacrylate, C14 alkyl methacrylate, C16 alkyl methacrylate, C18 alkyl methacrylate, and C8 alkyl methacrylate monomers.

7. The method according to claim 1 , wherein the lubricant composition comprises from 50 to 10000 ppm by weight of active material of copolymer (C) relative to the total weight of the composition.

8. The method according to claim 1 , wherein the engine is a marine engine.

9. The method according to claim 1 , for reducing the quantity of lubricant composition in the combustion chamber of the engine.

10. A method to reduce and/or control abnormal gas combustion in an engine, comprising the lubrication of the engine with a lubricating oil comprising:

at least one base oil;

at least one copolymer (C) such as defined in claim 1 .

11. Method to reduce the quantity of lubricant composition in the combustion chamber of an engine comprising the lubrication of the engine with a lubricating oil comprising:

at least one base oil;

at least one copolymer (C) such as defined in claim 1 .

12. Method to reduce and/or control abnormal gas combustion resulting from auto-ignition of the lubricant composition in an engine comprising the lubrication of the engine with a lubricating oil comprising:

at least one base oil;

at least one copolymer (C) such as defined in claim 1 .

13. The method according to claim 1 , wherein monomers (A) are 2-ethyl-hexyl methacrylate and/or monomers (B) are a mixture of C10 alkyl methacrylate, C12 alkyl methacrylate, C14 alkyl methacrylate, C16 alkyl methacrylate, and C18 alkyl methacrylate.

14. The method according to claim 1 , wherein the copolymer (C) comprises 55 to 70 weight % of C12 alkyl methacrylate and 20 to 30 weight % of C14 alkyl methacrylate relative to the total weight of monomers (B).