Vegetable oils are being considered as a renewable energy alternative for diesel fuel. Microemulsification can be used to reduce vegetable oil viscosity without complex chemical transformation processes. In this paper, a turbocharged common rail direct injection (CRDI) diesel engine was used to investigate the properties, performance, combustion and emission characteristics of the microemulsion fuels consisting of Tung oil, diesel, ethanol and surfactant. The experimental results presented that, with the volume fraction of ethanol increase, the viscosity and density of the microemulsion fuels were decreased and approached to that of diesel fuel. The ignition delay of the microemulsion fuels was longer than that of diesel fuel, and the curves of in-cylinder pressure, pressure rise rate and heat release rate showed different trend from that of diesel fuel. The brake specific fuel consumptions (BSFC) were slightly higher for the microemulsion fuels, but the brake thermal efficiencies (BTE) were also higher than those of diesel fuel. The microemulsion fuels showed evidently lower smoke emissions, but higher nitrogen oxides (NOx) emissions at high engine loads. The hydrocarbon (HC) and carbon monoxide (CO) emissions were slightly higher at low engine loads for the microemulsion fuels. (C) 2017 Elsevier Ltd. All rights reserved.