Niel gas engine. 19th-century artwork of a French design of gas engine known as a horizontal Niel engine. This design has two pistons, valves, and hot tube ignition. A gas engine is an internal combustion engine that runs on a gas fuel, such as natural gas, instead of the petrol used in car engines. 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 the first volume (1897) of 'La Revue Scientifique et Industrielle' by French chemist and inventor Jules-Louis Breton (1872-1940).