dieselization

Dieselization refers to the process of replacing earlier propulsion systems, such as steam engines or gasoline engines, with diesel engines across transportation and industrial sectors. The term is most often used in reference to railways and merchant shipping, but it also applies to road transport fleets and certain agricultural and industrial machines. Diesel engines offer improved energy efficiency, higher torque at low speeds, and longer range with simpler refueling logistics, factors that have driven widespread adoption since the early to mid-20th century. Environmental and economic considerations, including fuel availability and maintenance costs, have shaped the pace and geography of dieselization.

In the railway sector, dieselization began in the 1930s and accelerated through the 1950s and 1960s as diesel-electric locomotives replaced steam locomotives on many networks. Benefits included lower fuel consumption, reduced need for water and ash handling, easier operation, and greater reliability for longer runs. Electrification remains preferred in some routes, but diesel locomotives enabled more flexible operations on non-electrified lines and spurred modernization of rolling stock and yards.

Maritime propulsion also shifted toward diesel engines from steam and early gas turbines, particularly from the post–World War II era onward. Diesel-powered ships offered lower operating costs, simpler maintenance, and longer ranges for merchant fleets. Road transport and heavy equipment followed a similar trajectory, with diesel trucks, buses, and construction machinery becoming dominant due to energy efficiency and high torque.

Today, dieselization remains widespread but faces ongoing pressure from environmental regulations, fuel diversity, and the growth of alternative propulsion technologies such as electrification, hybrids, and liquefied natural gas in some sectors.