What is Automotive Thermal Efficiency?

[JoelAnn]

Automotive thermal efficiency refers to the ratio between the mechanical work output by the engine and the chemical energy generated from fuel combustion, which evaluates how much heat is converted into effective work. When the engine operates, only a portion of the thermal energy contained in the fuel is transformed into propulsion work, while the rest is lost in the form of heat or kinetic energy. Engine thermal efficiency is one of the indicators used to evaluate engine performance. The higher the thermal efficiency, the better the fuel economy, performance, and emissions. Fuel is never completely burned, as unburned portions remain hidden in carbon deposits and exhaust gases. Moreover, not all of the burned fuel necessarily converts into mechanical work. For example, fuel consumed during pre-ignition does not directly contribute to work output but can indirectly enhance the combustion efficiency of the power stroke.