What are the two main elements in fuel oil that produce most of its heat?

The two main elements in fuel oil that produce most of its heat are carbon and hydrogen. When fuel oil is burned, these elements undergo a chemical reaction with oxygen in the air, resulting in combustion.

During this process, carbon combines with oxygen to produce carbon dioxide, while hydrogen combines with oxygen to form water vapor. The chemical bonds that are broken and formed during this reaction release energy in the form of heat. This heat is what makes fuel oil an effective source of energy for heating systems and engines.

While other elements such as sulfur and chlorine may be present in fuel oil, they do not contribute significantly to the heat produced during combustion. Instead, they can lead to byproducts that may be harmful or require additional processing. Thus, it is carbon and hydrogen that are primarily responsible for generating the substantial heat output from fuel oil.