The diesel engine is an internal combustion engine that uses compression ignition, in which fuel ignites as it is injected into air in the combustion chamber that has been compressed to temperatures high enough to cause ignition. By contrast, petrol engines utilize the Otto cycle in which fuel and air are typically mixed before entering the combustion chamber and ignited by a spark plug, under which conditions compression ignition is undesirable (see engine knocking). The engine operates using the Diesel cycle named after German engineer Rudolf Diesel, who invented it in 1892 based on the hot bulb engine and for which he received a patent on February 23, 1893. Diesel had earlier experimented with the use of coal dust as a fuel in a similar design of engine. At the bequest of the French Government the Otto company demonstrated it at the 1900 Exposition Universelle (World's Fair) using peanut oil (see biodiesel). The French government were looking at using peanut oil for a locally produced fuel in their African colonies. Diesel later extensively tested the use of plant oils in his engine and began to actively promote the use of these fuels.
It is possible Rudolph Diesel was not first to invent the diesel. His patent (No. 7241) was filed in 1892. However, Herbert Akroyd Stuart and Charles Richard Binney had already obtained a patent (No. 7146) in 1890 entitled: "Improvements in Engines Operated by the Explosion of Mixtures of Combustible Vapour or Gas and Air" which described the world's first compression-ignition engine.. Akroyd-Stuart constructed the first compression-ignition oil engine in Bletchley, England in 1891 and leased the rights to Richard Hornsby & Sons, who by July 1892, five years before Diesel's prototype, had a diesel engine working for Newport Sanitary Authority. By 1896, diesel tractors and locomotives were being built in some quantity in Grantham. Importantly, Diesel's airblast injection system did not become part of subsequent 'diesel' engines, with direct-injection (DI) (as found in Akroyd-Stuart's engine) used instead, developed by Robert Bosch GmbH in 1927.