Correlating GDI and Diesel Soot with Carbon Black Surrogates: An MTM-SLIM Study

Legislations aimed at reducing CO₂ emissions are driving significant changes in passenger car engine hardware and lubricants. Gasoline direct injection (GDI) engines generate combustion soot which can drive wear which is characteristically different to that observed in diesel engines. The increasing market share of GDI engines has encouraged the auto OEMs and the oil suppliers to study this challenge in more depth and seek improvements which do not compromise the innate efficiency benefits of the GDI platform. This study compares soot abrasiveness by measuring the abrasive removal of Zinc dialkyldithiophosphate (ZDDP) antiwear films and resultant wear by GDI sooted oils and traditional Diesel sooted oils in the MTM-SLIM equipment. A three-way correlation has been developed between a carbon black soot surrogate, GDI sooted oils and Diesel sooted oils. Diesel sooted oils were found to be more abrasive and resulted in more severe wear than gasoline sooted oils at the same level of % soot loading. The impact of oil viscosity grade on soot induced wear has been observed. A thinner oil with lower soot concentration led to harsher wear conditions as compared to a thicker oil with higher soot loading. Both, thinner oils and increased soot loading led to increased wear levels, therefore both parameters need to be considered when wear data is being interpreted.