Actually it just keeps the engine at/close to minimal brake-specific fuel consumption: https://en.m.wikipedia.org/wiki/Brake-specific_fuel_consumption https://

Actually it just keeps the engine at/close to minimal brake-specific fuel consumption: https://en.m.wikipedia.org/wiki/Brake-specific_fuel_consumption https://en.m.wikipedia.org/wiki/Brake-specific_fuel_consumpt... Which covers a range of RPMs.