Today, many people are trying to find ways to run their cars on fuel that is better for the environment, cheaper and reusable. Bio-diesel is a fuel that is created by chemically reacting lipids or vegetable/animal fats with alcohol. Bio-diesel can only be used on cars that have diesel engines with converters. Bio-diesel has become so popular in recent years that it is being offered at the pump, alongside traditional diesel and petrol. Today many people are using bio-diesel because of the increased mileage per gallon, less dependence on foreign oil and the ability to make bio-diesel at home.