A diesel unit refers to a device or machine that runs on diesel fuel. Diesel engines are internal combustion engines that burn diesel fuel in order to generate power, and they can be found in various types of equipment such as generators, vehicles, boats, and heavy machinery. The term "diesel unit" is often used interchangeably with the phrase "diesel engine," but it can also refer to a complete piece of equipment that contains an internal combustion diesel engine, such as a truck or locomotive.