Purpose: To identify existing problems, namely the low homogeneity of the air-fuel mixture and fuel losses when valves are closed, and the advantages of central fuel injection, namely its relative ease of adjustment and location of gas injectors, and its main differences from distributed injection. To show existing ways to solve these problems. To demonstrate the lack of environmental and economic efficiency in central fuel injection. To calculate the amount of fuel entering the engine exhaust system when the valves are closed. To show ways to increase the efficiency of fuel utilization during engine operation. Methods: Calculation of the mass of natural gas entering the engine exhaust system during the valve overlap period, considering the duration of the period, the cross-sectional area of the valve gap, the total amount of fuel supplied during the intake stroke, the density of the fuel, the flow rate when entering the cylinder and the stoichiometric ratio. Results: The need to consider the amount of fuel consumed when operating a gas engine is shown. The existing problems of using central fuel supply are indicated. A method for calculating gas fuel losses when valves are closed is formulated and justified. It has been established which parameters influence the mass of fuel that does not enter the cylinder during the intake process. It is concluded that it is necessary to use other injection methods, or to significantly improve the intake process of central injection. Practical significance: The influence of the method of supplying fuel to a gas internal combustion engine on the environmental friendliness of the engine and fuel efficiency is shown. A method has been formulated for calculating gas fuel losses during the period of valve overlap, considering the design parameters of the intake system and the duration of opening of the intake valves.