The type of mineral oil used in transformers is typically a highly refined, low-viscosity mineral oil that possesses excellent electrical insulating properties, thermal conductivity, and stability. This oil is often devoid of significant impurities and additives that could compromise the performance or safety of transformer operations. Additionally, it is crucial for the mineral oil to have a high flash point and low pour point to ensure reliable operation under varying temperature conditions. The mineral oils used in transformers are specifically formulated to meet industry standards such as ASTM D3487, ensuring optimal performance in transforming electrical energy efficiently while providing adequate cooling and insulation.