The aim of the present work deals with the investigation of compression ignition characteristics for different concentrations of diethyl ether in diesel - Calophyllum Inophyllum Methyl Ester blends. Initially, various experiments were conducted for diesel, neat biodiesel, 50% blends of diesel and biodiesel at various engine loads with constant speed conditions. All the ternary blends were prepared by adding 5%,7.5%, 10% and 12.5% of diethyl ether with diesel-biodiesel blends. The addition of diethyl ether was limited by 12.5% by volume because the engine was not running at higher engine loads. The experimental study revealed that the brake thermal efficiency was reduced by 5.3% with increase in brake specific fuel consumption for 12.5% addition of diethyl ether in the blend when compared to diesel fuel. Further, the diesel engine operation with diesel-biodiesel-diethyl ether ternary blends has shown 84%, 4.6% and 57% reduction in unburned hydrocarbon, carbon monoxide and oxides of nitrogen emissions than that of diesel fuel at 100% engine load. The carbon dioxide emission formation was similar to diesel fuel at lower concentration of diethyl ether and 5.2% reduction was noted for higher fraction in the blend. Meanwhile, the smoke opacity has increased to 80.1% for 12.5% of diethyl ether addition in the blend. However, the combustion characteristics are slightly dropdown when the diesel engine was operated with all the ternary blends of diethyl ether.