CLAIMS
1. Cylinder lubricant for a two-stroke marine engine having a BN determined according
to the standard ASTM D–2896 greater than or equal to 15 milligrams of potash per gram
of lubricant, comprising:
(a) one or more lubricant base oils for marine engines,
(b) at least one detergent based on alkali or alkaline-earth metals, overbased with metallic carbonate salts,
(c) at least one neutral detergent,
(d) one or more oil-soluble alkoxylated fatty amines, and having a BN determined according to the standard ASTM D–2896 comprised between 100 and 600 milligrams of potash per gram,
where the percentage by mass of alkoxylated fatty amines with respect to the total weight of lubricant is chosen such that the BN provided by these compounds represents a contribution comprised between 2 and 8 milligrams of potash per gram of lubricant, and where the BN provided by the metallic carbonate salts represents a contribution of at the most 65% of the total BN, measured according to the standard ASTM D2896, of said cylinder lubricant.
2. Cylinder lubricant according to claim 1 where the BN of the alkoxylated fatty amines determined according to the standard ASTM D–2896 is comprised between 120 and 500, preferably between 150 and 400, preferably between 200 and 300 milligrams of potash per gram.
3. Cylinder lubricant according to one of claims 1 to 2 where the percentage by mass of alkoxylated fatty amines with respect to the total weight of lubricant is chosen such that the BN provided by these compounds represents a contribution comprised between 3 and 7 milligrams of potash per gram of lubricant, preferably between 3.5 and 5 milligrams of potash per gram of lubricant with the total BN of said cylinder lubricant, determined according to the standard ASTM D–2896.
4. Cylinder lubricant according to one of claims 1 to 3 having a BN, determined according to the standard ASTM D–2896, greater than or equal to 20, preferably greater than 30, advantageously greater than 40 milligrams of potash per gram of lubricant.

5. Cylinder lubricant according to one of claims 1 to 4 having a BN, determined according to the standard ASTM D-2896, less than 55 milligrams of potash per gram of lubricant.
6. Cylinder lubricant according to one of claims 1 to 5 having a BN, determined according to the standard ASTM D-2896, comprised between 40 and 50 milligrams of potash per gram of lubricant, preferably between 42 and 45 milligrams of potash per gram of lubricant.
7. Cylinder lubricant according to one of claims 1 to 5 having a BN, determined according to the standard ASTM D-2896, comprised between 50 and 55 milligrams of potash per gram of lubricant, preferably between 51 and 53 milligrams of potash per gram of lubricant.
8. Cylinder lubricant according to one of claims 1 to 7 where the BN provided by the metallic carbonate salts represents a contribution comprised between 10% and 60%, preferably between 20% and 55%, preferably between 30% and 50%, of the total BN of said cylinder lubricant.
9. Cylinder lubricant according to any one of claims 1 to 8 in which the oil-soluble alkoxylated fatty amine(s) are obtained from palm, olive, peanut, standard or oleic rapeseed, standard or oleic sunflower, soya or cotton oil, from beef tallow, or from palmitic, stearic, oleic or linoleic acid.
10. Cylinder lubricant according to any one of claims 1 to 9 in which the oil-soluble alkoxylated fatty amine(s) are obtained from fatty acids comprising between 16 and 18 carbon atoms.
11. Cylinder lubricant according to any one of claims 1 to 10 in which the alkoxylated fatty amine(s) correspond to general formula (I):
R2—(N R3 q— N—(-R1OH
fR1OJH (R1)H
V p V O (I)
where
R1 is an ethylene, propylene, butylene radical, preferably ethylene,
R2 is a fatty chain of saturated or unsaturated fatty acids, comprising between 12 and 22
carbon atoms, preferably between 16 and 18 carbon atoms, preferably the fatty chain of
oleic acid,

R3 is an alkylene radical comprising between 2 and 3 carbon atoms,
q is equal to 0 or to 1, and when q is equal to zero, p is equal to zero,
n, m and p are integers comprised between 0 and 12, preferably between 0 and 5,
preferably between 0 and 2,
and n + m + p is strictly greater than zero, preferably comprised between 1 and 15,
preferably between 2 and 10, preferably between 3 and 7, preferably between 3 and 4.
12. Cylinder lubricant according to claim 11 where:
• q = p = 0,
. m + n is comprised between 2 and 5, preferably between 3 and 4, . m and n are non-zero.
13. Cylinder lubricant according to any one of claims 1 to 12 in which the overbased detergents (b) and the neutral detergents (c) are chosen from the carboxylates, sulphonates, salicylates, naphthenates, phenates, and mixed detergents combining at least two of these types of detergents.
14. Cylinder lubricant according to one of claims 1 to 13 where at least one overbased detergent (b) is a sulphonate.
15. Cylinder lubricant according to one of claims 1 to 14 where at least one neutral detergent (c) is a phenate or a sulphonate, preferably a phenate.
16. Cylinder lubricant according to one of claims 1 to 15 also comprising from 0.1 to 10% by mass, preferably from 0.2 to 2%, preferably from 0.3 to 1.5%, preferably from 0.4 to 1%, preferably from 0.5 to 1% of one or more compounds chosen from:
. the primary, secondary or tertiary fatty monoalcohols, the alkyl chain of which is saturated or unsaturated, linear or branched, and comprise at least 12 carbon atoms, preferably between 12 and 24 carbon atoms, preferably between 16 and 18 carbon atoms, preferably the primary monoalcohols with a saturated linear alkyl chain,
. the esters of saturated fatty monoacids comprising at least 14 carbon atoms and alcohols comprising at the most 6 carbon atoms, preferably the mono- and diesters, preferably the monoesters of monoalcohol, and the diesters the ester functions of which are at most four atoms away counted from the oxygen side of the ester function.

17. Cylinder lubricant according to any one of claims 1 to 16, the kinematic viscosity of which measured according to the standard ASTM D445 at 100°C is comprised between 12.5 and 26.1 cSt, preferably comprised between 16.3 and 21.9 cSt.
18. Use of a lubricant according to any one of claims 1 to 17 as a single cylinder lubricant which can be used both with fuel oils with a sulphur content less than 1.5% m/m and with fuel oils with a sulphur content greater than 3.5% m/m in two-stroke marine engines.
19. Use of a lubricant according to any one of claims 1 to 17 as a single cylinder lubricant which can be used both with fuel oils with a sulphur content less than 1% m/m and with fuel oils with a sulphur content greater than 3% m/m in two-stroke marine engines.
20. Use of a lubricant according to any one of claims 1 to 17 as a cylinder lubricant which can be used with all the fuel oils with a sulphur content comprised between 0.1% m/m and 3.5% m/m in two-stroke marine engines.
21. Use of a cylinder lubricant according to one of claims 1 to 17 to prevent corrosion and/or reduce the formation of insoluble metallic salt deposits in the cylinders of two-stroke marine engines during the combustion of any type of fuel oil the sulphur content of which is less than 4.5% m/m.
22. Concentrate of additives, for the preparation of cylinder lubricants having a BN determined according to the standard ASTM D–2896 greater than or equal to 15, preferably greater than 20, preferably greater than 30, advantageously greater than 40 milligrams of potash per gram of lubricant, said concentrate having a BN comprised between 180 and 250, and comprising one or more alkoxylated fatty amines with a BN comprised between 100 and 600 mg of potash/g of amine according to the standard ASTM D–2896, the percentage by mass of said alkoxylated fatty amines in the concentrate being chosen so as to provide said concentrate with a contribution of BN determined according to the standard ASTM D–2896 comprised between 10 and 40, preferably between 12 and 30, preferably between 15 and 25, typically of the order of 20 milligrams of potash per gram of concentrate.