Straight Vegetable Oil vs. Biodiesel
The Advantages and Diasadvantages of Switching Fuels in a Diesel
Mar 24, 2009
There are things to consider before switching fuels on a diesel vehicle. There are advantages and disadvantages to using Straight Vegetable Oil vs. Biodiesel fuel. Straight Vegetable Oil conversions (SVO) involve vehicle modifications and may cause engine damage if not used properly. Biodiesel is more expensive due to more processing, but can be used in any Diesel engine without any modifications.
Using Straight Vegetable Oil in a Diesel Vehicle
Running a diesel on vegetable oil has some disadvantages. Vegetable oil is much more viscous than petroleum diesel fuel. Vegetable oil does not have the same chemical or combustion properties as diesel fuel and can damage engines.
Vegetable oil can be mixed with diesel, kerosene, or other fuels and solvents to improve viscosity of the oil. Vehicles using Straight Vegetable Oil should be used properly, some systems include two tank systems where the Straight Vegetable Oil is preheated. At start-up and shut-down the vehicle should be run on diesel or Biodiesel, the vegetable oil should only be used on hot engines. Shutting off a diesel engine running on Straight Vegetable Oil can cause the residue to crystallize in the cylinder and can cause problems.
During cold weather the vegetable oil crystallizes at higher temperatures than conventional diesel. This can cause cold staring problems and the crystals can block the fuel filter. Some diesel systems respond better to SVO than others. Direct Injection Diesels are not recommended for Straight Vegetable Oil, mechanical injection is much better for Straight Vegetable Oil. Copper should not be used in the fuel lines because it can catalyze the oil. When using SVO the quality and condition of the vegetable oil is more important than if it were to be processed for Biodiesel.
Biodiesel Fuel
According to the National Biodiesel Board, "Biodiesel is a domestic, renewable fuel for diesel engines derived from natural oils like soybean oil, and which meets the specifications of ASTM D6751." The ASTM standard ensures the opperator the quality of the Biodiesel fuel unlike SVO.
Vegetable oil can be used to make Biodiesel in a chemical process using methanol and other chemicals. Biodiesel is a clean burning, renewable fuel that can be used in any diesel vehicle without any fuel system or engine modifications. Biodiesel can be made out of different fats and oils used as base stocks to process into Biodiesel fuel.
Biodiesel has much better cold start up properties than SVO and can be most commonly found in blends called B20 – 20% Biodiesel, 80% Petroleum Diesel. Using Biodiesel helps reduce the amount of carcinogenic emissions that are caused by burning Petroleum based Diesel fuel.
Biodiesel has been tested more than Straight Vegetable Oil and many vehicle manufacturers in Europe now provide vehicle warranties for vehicle which run on straight Biodiesel fuel (B100). Biodiesel is becoming increasingly more popular in the United States and already is used by many European countries. In Germany, Biodiesel fuel is cheaper than Petroleum Diesel fuel.
