The present invention relates to lubricants for gas engines, preferably for stationary gas engines. The present invention relates more particularly to the use of a lubricating composition comprising at least one mineral base oil and at least one ester selected from esters of polyols for lubricating a gas engine, preferably for stationary gas engines. The present invention also relates to a method of lubricating a gas engine, preferably for stationary gas engines. Lubricants developed specifically for the lubrication of gas engines, preferably stationary gas engines have been known for several years. The first lubricants dedicated to this application contained group I base oils according to API classification. These lubricants showed good high temperature behavior, especially not formed or little deposit but had a limited resistance to oxidation, especially in the nitroxydation. By nitroxydation, oxidation is meant by contact with nitrogen oxides (NOx). Then the lubricants were incorporated Group II base oils according to API classification, to improve resistance to oxidation. However, and particularly gas engines of high power, the use of such lubricants has led to high temperature deposit formation (or varnish). It is the same for lubricants based on base oils of Group III and Group IV according to API classification. There is therefore a need for lubricating compositions for the gas engine lubricating, preferably for stationary gas engine, with good properties of detergency and therefore not forming or little deposition, especially at high temperatures while exhibiting oxidation resistance, including the nitroxydation, satisfactory or even improved. It has now been found that the combination of at least one mineral base oil and at least one ester selected from esters of polyols makes it possible to provide a lubricant composition dedicated for the lubrication of gas engines, preferably gas motors stationary, having a resistance to oxidation, including the nitroxydation, satisfactory or even improved and forming little or no deposits, especially at high temperatures. Thus, the invention provides a lubricating composition which can provide a solution to all or part of the problems of lubricating compositions for the lubrication of gas engines, preferably stationary gas engines. The present invention therefore relates to the use of a lubricating composition comprising at least one mineral base oil and at least one ester selected from esters of polyols for lubricating a gas engine. Surprisingly, the Applicant has found that the combination of at least one mineral base oil and at least one ester selected from esters of polyols in a lubricating composition for a gas engine, preferably for stationary gas engines allows improve the resistance to oxidation, including the nitroxydation, of the lubricating composition. Advantageously, the lubricating compositions according to the invention exhibit both a good resistance to oxidation, including the nitroxydation while reducing or eliminating, the formation of deposits, in particular at high temperature. Advantageously, the lubricating compositions according to the invention have good oxidation resistance properties, including the nitroxydation and detergency once implemented in a gas engine and in which the formulation is easy to implement. Advantageously, the lubricating compositions according to the invention have good oxidation resistance properties, including the nitroxydation and detergency once implemented in a gas engine while being stable over time, in particular storage-stable . In one embodiment of the invention, the gas engine is a stationary gas engine. In one embodiment of the invention, the mineral base oil is selected from a Group II base oil or a Group III base oil according to the API classification, preferably a group II Lower oil according to the classification API. In another embodiment of the invention, the lubricating composition comprises at least 50% by weight, preferably from 50% to 90% by weight of mineral base oil relative to the total weight of the lubricating composition. In another embodiment of the invention, the ester is chosen from esters of polyols and saturated or unsaturated carboxylic acids, linear or branched comprising at least 8 carbon atoms. In another embodiment of the invention, the carboxylic acid is a saturated monocarboxylic acid or unsaturated, linear or branched. In another embodiment of the invention, the carboxylic acid comprises 8 to 20 carbon atoms, preferably from 8 to 18 carbon atoms. In another embodiment of the invention, the polyol comprises at least three -OH groups, preferably from 3 to 8 -OH. In another embodiment of the invention, the polyol comprises from 3 to 10 carbon atoms. In another embodiment of the invention, the polyol ester comprises a mixture of at least a first ester of polyol and monocarboxylic acid as defined above and at least a second polyol ester and monocarboxylic acid as defined above and different from the first ester. In another embodiment of the invention, the ester is obtained by esterification reaction between a polyol as defined above, at least one first monocarboxylic acid as defined above and at least one second carboxylic acid selected from linear or branched dicarboxylic acids, saturated or unsaturated having at least 16 carbon atoms. In another embodiment of the invention, the lubricating composition comprises at least 2% by weight, preferably at least 5% by weight, polyol ester based on the total weight of the lubricating composition. In another embodiment of the invention, the lubricating composition further comprises polyisobutylene. The invention also relates to the use of at least one mineral base oil as defined above and at least one ester selected from polyol esters as defined above in a lubricating composition for lubricating a motor gas. The invention also relates to a method of lubricating a gas engine comprising contacting at least one motor mechanical parts with a lubricating composition as defined above. Detailed Description of the Invention The percentages given below are percentages by weight of active ingredient. The lubricating composition according to the invention comprises at least one mineral base oil. Mineral base oils used in the lubricating compositions of the invention may be oils of mineral origin belonging to groups I, II or III according to the classes defined in the API classification (or their equivalents according to the classification ATIEL) (Table A ) or mixtures thereof. Content Content Index saturated sulfur viscosity (IV) group 1 <90%> 80% 0.03