There have been recently many works on an utilization of biological resources, recovered from the sewage disposal and materials wastes. to energy and resources saving, but few works have been reported on the application of low quality biological gases to the automobile engine which requires the wide-range operation from low speed to high speed. Continued from the previous work, an investigation was made on the combustion of automobile engine using the above low quality biological gases by means of a possible device of gasoline engine and controlling air-fuel ratio, optimum ignition time, compressed ratio of the mixture. The results obtained were summarized as follows; (1) The chemical composition of the waste gases was averagely 60% methane, 38% carbon-dioxide and 2% others. (2) It found that the engine operation was possible even at the low methane content of 50% by controlling the air-fuel ratio. (3) An optimum condition for the combustion of biological gas was found to be 10 for the ratio of compressed mixture and B.T.D.C. 55° for ignition timing.