What is the difference between paraffinic and naphthenic transformer oil?

Paraffinic oils have higher wax content, higher pour points, and better oxidation stability, while naphthenic oils have naturally low pour points and better low-temperature fluidity. Naphthenic oils are widely used in transformers because they flow well in cold conditions without dewaxing. Paraffinic oils may require additives or processing to achieve similar low-temperature performance.