Nynas is well known globally for naphthenic mineral insulating oils often marketed under Nytro product families. In general terms, naphthenic transformer oils are selected for good low temperature flow properties and stable viscosity behavior, which supports cooling. They are also produced to meet standard transformer oil specifications, and are supplied with typical batch testing documentation used in utility procurement. The exact features depend on the specific grade and whether it is inhibited. For engineering selection, the important step is matching the oil grade to the transformer manufacturer requirements and the applicable standard and testing regime.