A review of the literature indicates that DBDS is usually found in concentrations ranging from 100 to
1000 mg/kg (ppm) in certain lubricating oils. DBDS is added to lubricating oils to protect against wear,
reduce friction and increase oxidation stability. Through a method developed at Doble to detect DBDS,
concentrations of 100 to 180 ppm have been found in new transformer oils but only in a small percentage
of products tested. Whether DBDS is formed as a result of the refining process, added or a combination
of both is unknown. The chemical structure of DBDS is found in Figure 1.