This work attempts to reduce the NOx emission of crude rice bran oil methyl ester with a marginal increase in smoke density and decrease in brake thermal efficiency in a stationary Cl engine. Three factors namely fuel injection timing, quantity of exhaust gases recycled and fuel injection pressures were chosen with three levels and their combined effect were investigated. Experiments were designed by employing design of experiments method and tests were conducted as per Taguchi's L-9 orthogonal array. Among the three, EGR is the most influencing factor at no load and part load to reduce NOx emission with less influence on smoke density while at full load fuel injection timing is more influential. Optimum combination level of factors was obtained by calculating multi response signal to noise ratio and simultaneously using Taguchi's parametric design and the obtained combination was confirmed through experiment. (C) 2012 Elsevier Ltd. All rights reserved.