Abstract: An ecological/fuel optimization device for internal combustion engines is provided, which increases a mass of moist air entering the engine by vacuum suction or normal aspiration. The device includes a container having a first compartment, including a room air inlet and an outlet for a mass of moist air. The room air inlet is connected to a central top portion of a buoy by a flexible pipe, the buoy including an air passage orifice, which carries air entering through the flexible pipe towards a fluid column under the buoy; and a counterweight, the first compartment also including a guide and a closing element arranged on the central bottom portion of the first compartment. A second compartment surrounds the first compartment, in fluid communication with the first compartment at its bottom. The height of the second compartment is equal to the height difference between the first compartment and the buoy.