Optimization of process conditions for biodiesel production through methanolysis of Indian mustard oil (MO) using magnesium-impregnated, precalcined fly ash heterogeneous base catalyst has been performed, using response surface methodology based on a four-factor, three-level face-centered central composite design. A quadratic polynomial model was formulated for estimation of biodiesel (fatty acid methyl ester, FAME) yield by multivariate regression analysis. Optimal parametric values corresponding to maximum experimental FAME yield (i.e., 97.5 wt %) were as follows: methanol:MO molar ratio, 13.13:1; calcination temperature, 950 degrees C; catalyst concentration, 3.44 wt?%; and stirrer speed, 890 rpm. The optimal magnesium base catalyst possessed a BET specific surface area of 9.07 m(2)/g, a catalyst pore volume of 0.0255 cm(3)/g with a modal pore diameter of 6.5 nm, and appreciable (11.52 mmol HCl/g catalyst) catalyst basicity. The formulated B10 biodiesel conformed to ASTM/European specifications. Thus, the optimally prepared low-cost and reusable catalyst can craft economical avenues for fuel-grade biodiesel synthesis from mustard oil.