The Use of TEOST(R) MHT-4 to Measure the Phosphorus Volatility of Engine Oils

The Use of TEOST(R) MHT-4 to Measure the Phosphorus Volatility of Engine Oils

Phosphorus is known to poison the exhaust gas catalysts used to control emissions in modern gasoline-fueled passenger car vehicles. Phosphorus volatility has been studied by others as a potential issue related to the compatibility of modern engine oils with exhaust gas catalysts using a modified version of the ASTM D5800 (Noack) test as well as the Sequence ⅢG engine test (ASTM D7320). The level of phosphorus volatility in these tests has been shown to be strongly affected by the chemistry of the zinc dialkyldithiophosphate (ZDDP) used in the engine oil formulation. The TEOST MHT-4 test (ASTM D7097) is a high temperature deposit test currently included in the ILSAC GF-4 specification. This bench test simulates the oxidation and deposit-forming characteristics of engine oils in the hot zones of modern high-performance engines and, therefore, was chosen by the author(s) as a tool to investigate differences in phosphorus volatility of modern engine oils. Our investigations demonstrate that the TEOST MHT-4 test is capable of measuring phosphorus volatility of engine oils with very good discrimination and precision; it may be considered for use in future ILSAC standards (e.g. GF-5).