Sulfates are formed as a result of combustion of sulfur-containing fuels, and can contribute to oil pollution and acid formation. In marine engines and plants with diesel operation, this is especially relevant.
Sulfate content is typically measured through FTIR or chemical degradation and titration. The amount provides a good measure of the strain the oil is subjected to.
The result is used to monitor oil aging and to assess the need for shorter oil change intervals, especially when using fuels with high sulfur content.