Gas engine piston. Historical illustration of sections through the piston of a gas engine, showing the connecting rod and the trunnion shaft. At top is a horizontal section, with a vertical section at centre. At bottom is a view looking down on the piston and its tightening mechanism. A gas engine is an internal combustion engine that runs on a gas fuel. Gas engines are usually used in heavy-duty industrial settings, such as factories. The first practical gas engines were developed in the 1860s. Artwork from 'Moteurs' (1911) by French civil engineer Max de Nansouty (1854-1913), part of the 'Les merveilles de la science' series of 1867-1891 by Louis Figuier.