Many people are still unaware that oil can be recycled. Oil is sometimes illegally poured down drains where it can be a serious pollution problem, instead of returning it to garages or local authority collection points. Even a few litres of oil spilled into a lake can produce a thin film over thousands of square metres and kill plants and animals. A refining company can produce up to 3,500 litres of usable oil from every 5,000 litres of processed waste oil. It can be used as a lubricating oil or further processed for use as a heating oil.