Detroit Diesel Corporation (DDC) is an American diesel engine manufacturer headquartered in Detroit, Michigan. It is a subsidiary of Daimler Truck North America, which is itself a wholly owned subsidiary of the multinational Daimler Truck AG. The company manufactures heavy-duty engines and chassis components for the on-highway and vocational commercial truck markets. Detroit Diesel has built more than 5 million engines since 1938, more than 1 million of which are still in operation worldwide. Detroit Diesel's product line includes engines, axles, transmissions, and a Virtual Technician service.

MTU Friedrichshafen GmbH is a German manufacturer of commercial internal combustion engines founded by Wilhelm Maybach and his son Karl Maybach in 1909. Wilhelm Maybach was the technical director of Daimler-Motoren-Gesellschaft (DMG), a predecessor company of the German multinational automotive corporation Daimler AG, until he left in 1907. On 23 March 1909, he founded the new company, Luftfahrzeug-Motorenbau GmbH, with his son Karl Maybach as director. A few years later the company was renamed to Maybach-Motorenbau GmbH, which originally developed and manufactured diesel and petrol engines for Zeppelins, and then railcars. The Maybach Mb.IVa was used in aircraft and airships of World War I.