In this work, with the aim of selecting the optimal operating conditions of a diesel engine (with regard to load and biodiesel blend) besides reducing both main exhaust emissions and BSFC (brake-specific fuel consumption) a methodology based on multiple response optimization has been proposed. BSFC and emissions (NOx, SO2 and CO) using three different load conditions (50%, 75% and 100%) using similar olive pomace methyl esters/diesel blends have been evaluated. Engine testing was followed by the design of the global desirability function in terms of both engine load and biodiesel blends. Eventually, a direct correlation between emissions and load was found. Finally, to ensure minimum values of BSFC under three levels of emissions reduction (10%, 20% and 40%) optimum engine operating ranges, in terms of load rate and biodiesel blends, are studied. (C) 2016 Elsevier Ltd. All rights reserved.