Why is inhibited transformer oil used to reduce oxidation?

Inhibited transformer oil contains oxidation inhibitors that slow the chemical reaction between oil, oxygen, and heat. Oxidation produces acids and sludge that lower interfacial tension, increase conductivity, and block cooling ducts. Inhibitors extend oil life, reduce deposit formation, and help maintain stable dielectric properties under normal operating temperatures. Inhibited oils are often preferred for free breathing transformers or higher thermal stress applications where oxygen exposure and aging rate are higher.