Castor oil is more than just a raw material in great demand by the pharmaceutical and chemical industries. A few properties, in particular the extremely high viscosity and high water content, complicate the use of straight castor oil as a fuel for internal combustion engines. A better perspective may be possible by transesterification and the addition of this biodiesel to fossil diesel fuel.
Castor oil had its own advantages as one of the promising sources of feedstock for biodiesel production despite having high viscosity compared to other vegetable oils. Castor oil does not contain sulfur; it has a greater cetane number which indicates a better quality of ignition and more oxygen content which promote more complete combustion. Castor oil has improved lubricity over other oils with similar carbon chain-length fatty acids. The hydroxylated fatty acids of ricinoleic acid in castor oil impart it better performance as a lubricity enhancer than other common vegetable oil esters. Castor biodiesels have a very low cloud point and pour point compared to other biodiesels which made it the best fuel for cold weather. Castor oil is distinguished by its high content of ricinoleic acid. No other vegetable oilcontains such a high proportion of fatty hydroxy acids.