The present research work deals with the application of 30% exhaust gas recirculation (EGR) in a direct injection compression ignition engine fuelled with 100% waste cooking oil methyl ester and conventional diesel. In the first phase of this research work, the performance, emission and combustion characteristics of diesel engine are investigated with the supply of fresh air–fuel mixture for conventional diesel and waste cooking oil methyl ester as fuels and in the second phase the fresh air–fuel mixture is blended with 30% exhaust gas. The study reveals that the 30% EGR addition decreased the brake thermal efficiency by 8 and 18% for conventional diesel and 100% waste cooking oil methyl ester as fuels. Nitrogen oxides emission is reduced to a great extent by 47.5% for diesel fuel and 58.9% for biodiesel fuel at full load condition. Further, the 30% EGR has substantially increased the carbon monoxide and unburnt hydrocarbon emissions for both the fuels at maximum brake mean effective pressure. In addition similar pattern of in-cylinder gas pressure, heat release rate, cumulative heat rate have been observed for fresh air fuel mixture and 30% EGR under various loading conditions. © 2018, Springer Science+Business Media B.V., part of Springer Nature.