Diesel fuel is a type of fuel derived from crude oil, primarily used in diesel engines. It is denser and contains more energy per liter than gasoline, making it efficient for heavy-duty vehicles like trucks and buses. Diesel engines operate using a different combustion process, which allows them to achieve better fuel economy and lower carbon dioxide emissions. The production of diesel fuel involves refining crude oil through distillation and other processes. It can also be made from renewable sources, such as biodiesel, which is produced from vegetable oils or animal fats. This alternative helps reduce reliance on fossil fuels and lowers greenhouse gas emissions.