The neat thing about biodiesel is that it can run in existing diesel engines with little or no modification to the engine or its fuel system. Performance is the same. However, some biodiesel vehicles are sluggish in cold climates. Since most vegetable oil is high in saturated fat, ice crystals tend to form in the biodiesel causing a vehicle's engine to struggle. However, biodiesel made from certain types of vegetable oil, such as canola (a form of rapeseed), is lower in saturated fat, which makes it harder for ice to form in frigid temperatures [source: University of Connecticut]. Biofuels help engines last longer, too. Oil has a high viscosity rate. Tests show that high biodiesel blends above B10 (10 percent biodiesel, 90 percent petroleum diesel) do not impact the vehicle's engine performance [source: Biodiesel.org].