Transesterifications of 6 vegetable oil samples in supercritical methanol (SC MeOH) were studied without using any catalyst. Methyl esters of vegetable oils have several outstanding advantages among other new-renewable and clean engine fuel alternatives. The variables affecting the methyl ester yielded during the transesterification reaction, such as the molar ratio of alcohol to vegetable oil and reaction temperature, were investigated. Compared to No. 2 diesel fuel, all of the vegetable oils are much more viscous, while methyl esters of vegetable oils are the slightly more viscous. The methyl esters are more volatile than those of the vegetable oils. The soaps obtained from the vegetable oils can be pyrolyzed into hydrocarbon-rich products.