Fossil fuels are actually stored chemical energy. This energy is potential energy which is accessed when combustion occurs. Ancient microscopic organisms became buried and conditions of heat and pressure, were changed into the oil and gasoline we use today. The fuel is burned and the energy which was stored in the chemical bonds is then released. It can then be converted to mechanical energy, kinetic energy, heat energy and electrical energy within the car's machinery. This illustrates the idea that energy is not created nor destroyed, however, it can change form and the total amount is conserved.