In cities across the globe, the personal automobile is the single greatest polluter as emissions from millions of vehicles on the road add up to a planet-wide problem. Vegetable oils have become more attractive recently because of their environmental benefits and the fact that they are made from renewable resources. With recent increases in petroleum prices and uncertainties concerning petroleum availability, there is renewed interest in vegetable oil fuels for diesel engines. The biodiesel impacts oil exhaust emissions varied depending on the type of biodiesel and oil the type of conventional diesel. Blends of up to 20% biodiesel mixed with petroleum diesel fuels can be used in nearly all diesel equipment and are compatible with most storage and distribution equipment. Using biodiesel in a conventional diesel engine substantially reduces emissions of unburned hydrocarbons, carbon monoxide, sulfates, polycyclic aromatic hydrocarbons, nitrated polycyclic aromatic hydrocarbons, and particulate matter. These reductions increase as the amount of biodiesel blended into diesel fuel increases. In general, biodiesel increases NOX emissions when used asjuel in a diesel engine. The fact that NOX emissions increase with increasing biodiesel concentration could be a detriment in areas that are out of attaininentfor ozone.