Sulphur emissions from engine oil: Information from the sulphur emission index

Data published by the Institute of Materials including information on the volatility, sulphur content, and sulphur volatility of 913 engine oils were compiled. These engine oils were collected in three geographic regions: North America, Europe, and Asia. The volatility data were generated using a Selby—Noack instrument in which all volatilised material is collected for the further analysis of phosphorus and sulphur content. It was found that under the normal Noack test exposure conditions of 250°C for one hour, the sulphur emission index (a measure of sulphur volatility in mg/l) varied markedly among the engine oils. In a correlation study, a minor correlation of up to %R2= 15 was found between sulphur volatility and oil volatility while a greater correlation of up to %R2 = 39 was found between sulphur volatility and sulphur content of the formulated engine oils. A new concept and application of the sulphur volatility ratio may be useful in explaining the observations concerning sulphur volatility dependence.