Vegetable oils and animal fats in their raw form have high viscosities that makes them unsuitable as fuels for diesel engines. Transesterification is one of the well-known processes by which fats and oils are converted into biodiesel. The reaction often makes use of acid/base catalyst. If the material possesses high free fatty acid then acid catalyst gives better results. In the present investigation, Mahua oil having 14% free fatty acid was transesterifed to obtain biodiesel using acid catalysts with different alcohols. The alcohols used were Methanol, Ethanol and Butanol. The objective of using higher alcohol is to find their effect on ester yield. The process optimization was made based on the maximum ester yield. The results show that transesterification with butanol gives a better yield compared to methanol and ethanol. The transesterification results show that higher catalyst concentration by 6-10% Vol. produces biodiesel with lower viscosity, lower specific gravity with a higher yield (short reaction time of 5 hours). The best process condition with butanol was found to be 6% Vol. of sulfuric acid with 150% excess butanol, which gave an yield of around 95.4% in a reaction time of 5 hours. The prepared biodiesels were tested as per the standard and were found to be satisfactory. (C) 2010 Elsevier Ltd. All rights reserved.