The possibility of high sulfate emissions from future emission control systems prompted an evaluation of a low sulfate system designed to meet 1981 emission standards. An air injected oxidation catalyst was added to a Volvo “Lambda-Sond” emission control system. After baseline determination of gaseous and sulfate emissions, the air injection system was modified to reduce sulfates. Optimization tests determined the best air injection schedule for sufficient CO control while limiting sulfate production. A sulfate reduction of 99 percent was achieved. The system was then durability tested for 64,400 km.