Diesel trains do not use diesel to start up their engines. Instead, they use a separate starting engine, which is typically powered by an electric battery or a small diesel generator. The starting engine is used to turn the main diesel engine over until it starts running on its own. Once the main engine is running, the starting engine is disengaged.
The amount of diesel that a train uses to start up the engine is therefore negligible. In fact, most modern diesel trains do not even have a starting engine. Instead, they use an electric motor to start the main diesel engine. This is more efficient and reliable than using a separate starting engine.
