Catalyst durability tests were run to gain additional information on the effects of contaminants on catalyst deterioration. Six different fuels were used with two oxidizing bead catalysts-platinum and palladium. In addition, a special oil was evaluated with both catalysts.Both catalysts showed deterioration with miles, but the platinum catalyst had least deterioration. Increasing lead in fuel increased deterioration. Increasing sulfur did not. Phosphorus, however, was harmful, more so with the platinum catalyst than the palladium.