A gas engine is an internal combustion engine which uses blast furnace gas, producer gas, natural gas and others as fuel. The first practical gas engine was built in 1860 by a Frenchman named Lenoir, but as it was largely improved by Dr. Otto, his name was given to its cycle of operations. He made his first gas engine in 1876. The Otto cycle utilizes an ignition source such as a spark or small amount of pilot fuel to start the gas fuel burn.