The addition of specific fatty acids or fatty acid esters has proven to enhance diesel fuel lubricity.7 Moreover, the addition
of biodiesel improves the lubricity of low sulfur diesel fuel even more than pure fatty esters,8 meaning that different fatty acid esters show synergistic effects when they are mixed. Anastopoulos et al.7 found that the addition of biodiesel, independently of the raw material, improves the lubricity more than other fatty acid derivatives (lauric diethylamide and palmitic dibutylamide) when they were added to two different lowsulfur diesel fuels.Additionally, they did not find major differences between different biodiesel fuels in the corrected wear scar. Other studies have found that there are no appreciable differences between fatty acids as lubricity enhancers, except with the hydroxylated ones whose OH group makes them more effective as a wear protector.9-15 Goodrum and Geller11 found that the effect of the oil feedstock was minor when biodiesel fuels were added in concentrations around 5%. However, the addition of biodiesel produced from hydroxilated oils, such as lesquerella and castor oils, reduced the wear scar much more sharply (with less than 1% concentrations) than in the case of nonhydroxylated oils (rapeseed and soybean).