Interests on vegetable oils as replacement of mineral oil in power apparatus are growing in recent years due to their better environmental performance and higher fire safety guarantee. The major aim of this research work is to identify a suitable high performance, eco-friendly, biodegradable vegetable oil as a dielectric fluid for transformer and other power apparatus applications. Having this in view, the key objective is to perform the laboratory experiments as per International Electro technical Commission test procedures to understand the Lightning Impulse Voltage Characteristics and other thermo-physical characteristics of various vegetable oils such as palm oil and coconut oil under both virgin and aged conditions. Vegetable oils are at least 97% biodegradable and its spillage causes no harm to the environment. Also the oils are easily available. In order to identify a suitable vegetable oil as an alternate for conventional mineral oil, experimental results are compared with the mineral oil and reported in this paper.