Formulation Impacts on Sequence IIIG Viscosity Increase 2007-01-1961

A range of tools including analytical, bench, and engine tests have been used to investigate the viscosity increase mechanism and formulation appetite of the Sequence IIIG engine test. As commonly observed with high temperature tests, the Sequence IIIG has a strong appetite for antioxidants. Base oil also has a strong impact. Base oil volatility has a direct physical impact on viscosity due to the evaporation of light base oil components and the resultant increase of non-volatile additive components. Volatility characteristics are dependent on the distribution of volatile fractions. The relative oxidation and volatility contributions to viscosity increase have been compared between the Sequence IIIG and Sequence IIIF. The impact of base oil volatility is greater in the Sequence IIIG than the Sequence IIIF test.