How can a reliable transformer oil supplier be selected?

Choose suppliers that can demonstrate compliance with the required standards (IEC 60296 for mineral oils or the specified ester or silicone standard), provide consistent certificates of analysis, and support traceability by batch. Evaluate storage and handling practices, moisture control, delivery filtration options, and technical support. For utilities, also consider multi site production continuity, local availability, and proven performance references. Require SDS, test limits, and acceptance testing procedures before first fill and for future top ups.