Diesel fuel is a type of fuel derived from crude oil, primarily used in diesel engines. It is heavier and denser than gasoline, which allows it to provide more energy per liter. Diesel engines are commonly found in vehicles like trucks, buses, and some cars, as well as in machinery and generators. The production of diesel fuel involves a refining process that separates and transforms hydrocarbons. It is known for its efficiency and longevity, making it a popular choice for long-distance transportation. However, diesel fuel can produce higher levels of nitrogen oxides and particulate matter, which can contribute to air pollution.