This process pertains to a achieving high on-stream time and maintaining the temperature and composition of the raw effluent gas stream from a partial oxidation gas generator being fed simultaneously with a stream of gaseous fuel and separate stream of liquid hydrocarbonaceous fuel. Two parallel oxygen streams equipped with flow transmitters and control valves are used to supply the oxygen associated with two separate and different fuel streams. Each stream of oxygen is controlled by an O.sub.2 /fuel ratio control so that if the flow rate of either stream of fuel or its related oxygen stream changes, the oxygen/carbon atomic ratio of the remaining O.sub.2 and fuel stream in the gasifier is maintained at a desired value. Further, if either fuel flow is stopped, its associated O.sub.2 flow will stop, but the remaining fuel stream and its associated O.sub.2 stream will continue to flow at the same rate with no change in the oxygen/fuel weight ratio. Complete shut down of the unit is thereby avoided. The quick raising of reactor temperatures to unsafe levels due to excess oxygen that occurs when one of the fuel streams is lost is thereby prevented.