What are common commercial names of transformer oils used worldwide?

Common commercial names include mineral oil brands and ester fluid brands supplied by large oil and specialty chemical companies. Examples often seen in the market include Shell Diala series, Nynas Nytro series, and other mineral insulating oils from major refiners, as well as natural ester and synthetic ester fluids used for fire safety and environmental performance. Many regions also have strong local brands. In procurement, utilities typically specify compliance to standards and approve certain vendor lists rather than relying only on brand names, to ensure consistent quality and documentation.