The paper presents a new and original internal-combustion engine. It is presenting a method for determining the kinematics and the efficiency of a new mechanism, MF1, proposed (designed) to work and be tested like an internal-combustion engine. One determines the mechanical momentary efficiency, when the mechanism works like a steamroller and when the mechanism works like a motor. The determined efficiency is different in the two described situations. One presents an original way to determine the dynamic efficiency too. The dynamic momentary efficiency is the same in the two situations: when the mechanism works like a steamroller and when it works like a motor. One determines the efficiency without friction, but one can anytime add the effect of friction modulus. One presents the dynamic kinematics of this mechanism too: the dynamic velocity and the dynamic acceleration. When the constructive parameters are normal, the dynamic velocities take the same values like the classical speeds and the dynamic accelerations take the same values like the classical accelerations.