An evaluation of gaseous fuels was made to determine their capability in reducing emissions from automobiles. The four-part program included tests of propane (LPG) and natural gas in a dynamometer engine (phase one) and in a car parameter study (phase two). Power and spark requirements were compared with those of gasoline on the dynamometer engines. Emissions, economy, performance, and drivability were evaluated on the cars; and air-fuel ratio, spark advance, and exhaust gas recirculation served as variable parameters.The third phase of the program determined the low-emission capability of an LPG car with proposed emission hardware. The economy, performance, and drivability at these low levels were obtained.The final phase tested a dual-fuel car to evaluate the feasibility of using LPG to start and warm up the car, followed by an automatic switch to gasoline. The emissions, drivability, and the LPG fuel consumption were recorded.