Volatility of a base oil and individual additives such as phosphorus can be measured separately, and it makes sense to hypothesize that significantly reducing phosphorus volatility would significantly reduce catalytic convertor poisioning. An extensive 2001 study of 1,300 oils by Ted Selby of "Savant" concluded that the volatility of engine oil itself is not related to phosphorus emissions and the proper phosphorus chemistry and formulation can effectively reduce phosphorus volatility and emissions.
Selby proposes that engine oils can be formulated so that the antiwear properties of phosphorus are maximized, while the negative effects of catalyst poisioning are minimized. Selby developed the "Phosphorus Emission Index" or PEI, to compare the volume of phosphorus in volatized oil to the volume in the fresh oil. Higher PEI numbers indicate more phosphorus volatility per volume of fresh oil.
Ford recently conducted a study of 20 New York taxicabs. Each taxicab was driven for 100,000 miles, with the oil changed at 3000 mile intervals in the beginning and 5000 mile intervals later in the test. According to Milt Johnson of Ford, "Of the total amount of phosphorus that was lost from the oils during the 100,000 miles, the fraction that could be attributed to selective volatilization of phosphorus ranged from 56 to 87 percent. The volatility of engine oil phosphorus was a major contributor to phosphorus loading on the catalyst."
"Fords data suggested that up to 80 percent to 85 percent of the phosphorus that was getting to the catalyst was coming from volatile phosphorus rather than from direct oil consumption," added Rich Lee of Chevron Oronite. "But the data also showed that with high oil consumption, as found with non-detergent oil, the source of the phosphorus on the catalyst was more like 50/50 - half from the direct oil consumption, half from volatile phosphorus. While limits on phosphorus volatility and bulk oil phosphorus may be appropriate, the ideal solution would be a catalyst performance test."
Selby proposes that engine oils can be formulated so that the antiwear properties of phosphorus are maximized, while the negative effects of catalyst poisioning are minimized. Selby developed the "Phosphorus Emission Index" or PEI, to compare the volume of phosphorus in volatized oil to the volume in the fresh oil. Higher PEI numbers indicate more phosphorus volatility per volume of fresh oil.
Ford recently conducted a study of 20 New York taxicabs. Each taxicab was driven for 100,000 miles, with the oil changed at 3000 mile intervals in the beginning and 5000 mile intervals later in the test. According to Milt Johnson of Ford, "Of the total amount of phosphorus that was lost from the oils during the 100,000 miles, the fraction that could be attributed to selective volatilization of phosphorus ranged from 56 to 87 percent. The volatility of engine oil phosphorus was a major contributor to phosphorus loading on the catalyst."
"Fords data suggested that up to 80 percent to 85 percent of the phosphorus that was getting to the catalyst was coming from volatile phosphorus rather than from direct oil consumption," added Rich Lee of Chevron Oronite. "But the data also showed that with high oil consumption, as found with non-detergent oil, the source of the phosphorus on the catalyst was more like 50/50 - half from the direct oil consumption, half from volatile phosphorus. While limits on phosphorus volatility and bulk oil phosphorus may be appropriate, the ideal solution would be a catalyst performance test."
