A method is provided for turning down or up the output of raw product gas from a partial oxidation gas generator while maintaining in an acceptable range the efficiency of the gas generation, or conversion of the fuel to gas, and the quality of the gas produced. In the process, the flow rates for the separate feedstreams to the burner comprising fuel optionally in admixture with a temperature moderator, at least one stream of free-oxygen containing gas optionally in admixture with a temperature moderator, and with or without a separate feedstream of temperature moderator are adjusted down or up a predetermined amount to obtain a specified output of raw product gas while maintaining substantially constant in the reaction zone the levels of O/C atomic ratio and the temperature moderator/fuel weight ratio. Further, the temperature of at least one stream of free-oxygen containing gas optionally in admixture with a temperature moderator is increased at turn-down and decreased at turn-up to a predetermined value which is an indirect function of its adjusted flow rate. By this means, the burner tip velocity of the temperature adjusted stream of free-oxygen containing gas optionally in admixture with a temperature moderator is held within an acceptable range, and changes in the process efficiency and pressure drop across the burner are minimized.