Diesel locomotive

A diesel locomotive is a locomotive powered by a diesel engine. The diesel engine drives the locomotive's wheels through a transmission system. Diesel locomotives are very popular worldwide, due to their ease of use and reliability. They can be more powerful than steam locomotives and do not need an expensive power grid like electric locomotives.
Transmission systems.
Through a gearbox, shaft or chain (diesel-mechanical)
By generating electricity which is in turn used to power the wheels (diesel-electric). This is the kind most used.
By using a hydraulic transmission system (diesel-hydraulic)