Fuel oil is a type of petroleum product used primarily for heating and powering engines. It is derived from crude oil through a refining process and is commonly used in industrial applications, marine vessels, and residential heating systems. Fuel oil is categorized into different grades, with the most common being No. 2 fuel oil, which is often used in homes and commercial buildings. The combustion of fuel oil produces energy, but it also releases emissions, including carbon dioxide and sulfur dioxide. To mitigate environmental impacts, regulations have been established to limit the use of high-sulfur fuel oils. Additionally, alternative energy sources are being explored to reduce reliance on fossil fuels.