What is the chemical classification of transformer oil?

Most traditional transformer oil is a petroleum derived mineral insulating oil composed mainly of hydrocarbons, often classified as naphthenic, paraffinic, or mixed base depending on refining. Alternatives include natural ester fluids (vegetable based triglycerides), synthetic esters, and silicone fluids. Chemically, mineral oil is a mixture rather than a single compound, so it does not have one formula. Classification in safety documents typically includes hazard class, flash point category, and environmental handling rules rather than a single chemical identity.