In this case, the fuel value is defined as the amount of energy released by the complete combustion of 1g of a particular mass of the substance called fuel. In such a way, the higher the energy density (fuel value) the less energy is used transporting the fuel.
Specific heat and heat capacity lead to the necessary heat to increase the temperature of 1g of a substance by 1°C. Enthalpy is a thermodynamic quantity related with the total heat content of a system. Nutritional calorie content is the energy provided by a food and heat capacity
