Abstract: In accordance with the proposed method the combustible mixture fed to the engine is formed from a petrol-air flow and a hydrogen-air flow. Depending on the load on the engine shaft the composition of the combustible mixture is controlled by varying the amount and composition of said mixtures in said flows so that at full load the resulting combustible mixture contains (by weight) from 5.8 to 6.0% of petrol, from 0.14 to 0.17% of hydrogen, and from 93.7 to 94.0% of air, and a load constituting 0.1 of the full load, said mixture contains from 1.2 to 1.5% of petrol, from 0.42 to 0.45% of hydrogen, and from 98.1 to 98.4% of air. There are also given the quantities of the components in said combustible mixture for other load conditions.