Petroleum/pəˈtrəʊliəm/ Definition 1 of 3Pro Tip 1/3Energy Fuel Petroleum often refers to energy sources like gasoline and diesel. Gasoline derived from petroleum powers many vehicles. Pro Tip 2/3Industrial Use Petroleum is vital in industries, not just for fuel but for manufacturing. Factories rely on petroleum for producing various goods. Pro Tip 3/3Not Always Liquid Though it's an oil, petroleum can be refined into solid products. Petroleum can be found in waxes and asphalt.