How does transformer cooling oil dissipate heat under load?

Cooling oil circulates naturally by convection or is forced by pumps. Hot oil rises from windings and core, flows to radiators or heat exchangers where heat transfers to air or water, then cooler oil returns to the active part. Under heavy load, forced oil and forced air cooling may activate to increase heat removal. Efficient heat dissipation reduces hot spot temperature, slows paper aging, and prevents thermal runaway. Oil properties like viscosity and thermal conductivity influence cooling performance across seasons.