The transformer is a crucial component of every electrical substation. Its effective operation is essential for the seamless running of electricity systems. The shift from conventional crude mineral oils to eco-friendly natural esters is the main motive of the present research work. The present paper assesses several key factors that are crucial for figuring out the suitability of different insulating oils with respect to their physicochemical characteristics, breakdown voltage, fire resistance, environmental impact, water content, and oxidation stability. The paper also provides a comparative analysis of the various types of insulating oils used for power transformers. The present helps transformer experts for selecting appropriate oils in accordance with the requirements in the field.