This paper investigates the combustion, performance and emission characteristics of a single-cylinder diesel engine using neat biodiesel (Pongamia methyl ester) with two different blends (10% and 15% diethyl ether [DEE]) at different load conditions. The measured values of brake thermal efficiency (BTE), brake specific fuel consumption (BSFC), exhaust gas temperature (EGT), carbon monoxide (CO), hydrocarbon (HC), nitrogen oxide (NO) and smoke were calculated and analysed and compared with diesel fuel. The results showed that a significant reduction in NO and smoke emissions for neat biodiesel with 15% DEE blend compared with neat biodiesel at full load conditions. The peak pressure and heat release rate were decreased, and maximum rate of pressure rise and ignition delay were also decreased with DEE blends at full load. On the whole, it is concluded that the biodiesel with 15% DEE blend showed better results with respect to efficiency and emissions point of view compared with biodiesel. © 2016 Elsevier B.V., All rights reserved.