Number of experiments have been performed on various performance and emission characteristics, effect of biodiesel blends on lubricity and input and output energy distribution in diesel engine fuelled with biodiesel blends. It is also reviewed that energy audit is used in buildings, plants, process and equipments and energy audit method was developed for fishing vessels based on similar systems for land based industries. In land based businesses, industries and households, energy audits are presently used to investigate the use of energy and to identify opportunities for the efficiency improvement and effectiveness in the energy use. Energy audits have been used in various sectors, industries and utilities. This paper is a review paper of energy audit and it is found that there is a vast scope for implementation of standardized energy audit in diese engines fuelled with biodiesel blends. Its objective is to find out a standard energy audit method for diesel engine fuelled with biodiesel blends which evaluate the feasibility of biodiesel blend as fuel and also harmonise the research of biodiesel as fuel.