Engine Oil Phosphorus Effects on Catalytic Converter Performance in Federal Durability and High-Speed Vehicle Tests

Phosphorus derived from engine oil adversely affected catalyst performance monitored in two separate vehicle tests. In the first test, conducted using six matched vehicles operated at high-speed conditions with three different commercial engine oils, catalyst hydrocarbon conversion efficiency decreased linearly with both the amount of phosphorus added to the engine, and that found on the catalyst. In the second test, conducted using four matched vehicles operated on two different commercial engine oils using the Federal Durability Driving Cycle, hydrocarbon conversion efficiency also decreased linearly with the same phosphorus parameters. In this latter test, for nominal oil economies (3 400 km/ℓ) and phosphorus concentrations found in current oils (0.17 weight percent), catalyst deterioration due to phosphorus poisoning was greater than that due to thermal degradation and could adversely affect a vehicle's ability to pass current (1977) and future emission standards.