ENGINE FUELED WITH MIXED FUEL AND OPERATION CONTROL METHOD THEREOF

In an operation control method of an engine using a mixed fuel of a mixture of a plurality of fuels having different properties, operation condition of the engine being controlled according to a detection signal from a fuel blend ratio detector for detecting the blend ratio of the plurality of fuels in the mixed fuel, and when a malfunction occurs in the detection by the fuel blend ratio detector, the engine is provided with blend ratio storage for storing a plurality of emergency blend ratios for ignition timing control and for air fuel ratio control, and operation condition of the engine is controlled according to the plurality of emergency blend ratios.