Why is specific gravity important for transformer mineral oil evaluation?

Specific gravity is a quick indicator related to density and composition, which affects heat transfer, buoyancy driven oil circulation, and sometimes dissolved gas behavior. It is also used for quantity conversions between volume and mass for filling, transport, and inventory control. Changes from baseline can indicate contamination, mixing of different oil types, or severe aging. Specific gravity alone is not a health verdict, it must be interpreted with moisture, acidity, BDV, and DGA results.