Straight Vegetable Oil and Other Products

Raw or refined plant oils, fats, or recycled greases that have not been processed into biodiesel, such as straight vegetable oil (SVO), are not biodiesel and should be avoided. Research shows that plant oils, animal fats, and/or greases used in diesel engines, even at concentrations as low as 1%, can cause long-term engine deposits, ring sticking, lube oil gelling and other maintenance problems, and can reduce engine life. These problems are caused mostly by the much higher viscosity, or thickness, of the raw fats and/or oils (around 40 square millimeters per second [mm2/s]) compared to that of diesel fuel, for which the engines and injectors were designed (1.3 to 4.1 mm2/s). The significantly higher boiling point of raw fats and oils may also lead to failure of the fuel to fully evaporate, especially during cold start, leading to harmful engine deposits and engine oil sludging. Through the process of converting plant oils or greases to biodiesel by esterification, the viscosity and boiling point of the fuel are reduced to values more similar to conventional diesel fuel (biodiesel viscosity values are typically 4 to 5 mm2/s).

Other products, many of which are offered to consum-ers without the benefit of EPA registration, ASTM spec-ifications, or extensive testing and demonstrations, may be mislabeled as “biofuels,” “renewable diesel,” or even as “biodiesel.” It is up to the consumer to be aware of what they are purchasing. If you purchase methyl esters that do not meet ASTM biodiesel standards, it is not legal biodiesel and should not be used in diesel engines or other equipment designed to operate on diesel fuel. Methyl esters are used as an industrial lubricant and solvent in some applications, so be sure to purchase only ASTM D6751-grade methyl esters (biodiesel) for use in diesel engines.