Using Unmodified Vegetable Oils as a Diesel Fuel Extender – A Literature Review

This paper is a review of literature concerning using vegetable oils as a replacement for diesel fuel. The term vegetable oils as used in this paper refers to vegetable oils which have not been modified by transesterification or similar processes to form what is called biodiesel. The oils studied include virgin and used oils of various types including soy, rapeseed, canola, sunflower, cottonseed and similar oils. In general, raw vegetable oils can be used successfully in short term performance tests in nearly any percentage as a replacement for diesel fuel. When tested in long term tests blends above 20 percent nearly always result in engine damage or maintenance problems. Some authors report success in using vegetable oils as diesel fuel extenders in blends less than 20 percent even in long term durability studies. Degumming is suggested by one author as a way to improve use of raw oils in low level blends. It is apparent that few, if any, engine studies using low-level blends of unmodified vegetable oils, < 20%, have been conducted.