The diesel ingine (cried a compression-igneetion or 'CI' ingine an aa) is an internal combustion ingine in which igneetion o the fuel that haes been injectit intae the combustion chamber is initiatit bi the heich temperatur which a gas achieves when greatly compressed (adiabatic compression). This contrasts wi spark-ignition ingines such as a petrol ingine (petrol ingine) or gas ingine (uisin a gaseous fuel as opponed tae petrol), which uise a spark plug tae ignite an air-fuel mixtur.

NBL/MAN diesel ingine built by North British Locomotive Company