The present invention relates to the field of internal combustion engines having reciprocating piston motion and is useful in the automotive, aeronautic, and maritime industries, in generator sets, and in all other cases where an internal combustion engine with reciprocating piston motion is used as the main power source. Said invention makes it possible to substantially reduce power loss during the transmission thereof between the different parts of the engine, improves the conversion of the reciprocating piston motion into rotational movement, and to this end, increases the efficiency, adaptability, and power of said engine. The engine, in the optimal configuration thereof, comprises: four pistons; two peripheral transverse levers (1) hinged to one another by means of the connecting lever rod; a connecting moment rod; two handles; and a connecting power rod (12). Said invention relies on the low-oscillation peripheral transverse lever system to reduce power loss during the transmission thereof between two pairs of pistons (21). Moreover, said invention benefits most from optimizing the reciprocating motion of the pistons (21) into usable rotational movement through the use of the assembly of the dual handles and connecting moment rods. The moment arm (7) of the connecting moment rod harnesses the reciprocating motion of the pistons and generates a tangential force on the connecting power rod (8) of said moment arm such as to rotate the power handle (9) using the connecting moment rod and lever handle (10) assembly, and when the efficiency of said tangential force decreases, the connecting moment rod then generates a moment from the force generated by the piston at the other end thereof in order to continue rotating the power handle. A movement of the handle axis (18) from the lever handle (10) causes variation in the volume of the combustion chamber, and modulating the position of said axis makes it possible to consequently vary the compression rate of the engine. The harnessing of the energy released by the pistons is highest at the start of the decompression phase of the pistons and is kept at a high value until the end of the decompression. The rising phase of the piston is solely ensured by the inertia from the flywheel, which does not cause any problem, given the increase in the amount of energy stored during decompression and optimization of the efficiency of energy release by the flywheel. The engine of the present invention can operate with all types of commonplace fuel, such as gasoline, diesel fuel, heavy fuel, hydrogen, or LPG.