An emission control system for reducing total particulates and NOX emissions from the exhaust of a diesel engine includes an air supply system that supplies oxygen enriched air to an air intake of the engine. The air supply system may include a selectively permeable air separating membrane device for producing the oxygen enriched air. In order to effectively utilize the increase in the concentration level of oxygen in the intake air, the amount of fuel being supplied to the diesel engine also is increased at a minimum in proportion to the increased concentration level of oxygen in the intake air. The increase in the amount of such fuel being supplied to the diesel engine can be adjusted by an electronic fuel injection system used on such diesel engines. In addition, the electronic fuel injection system is used to retard the injection timing of the engine.