Abstract: An additive compound consisting of medium carbon alcohol, low carbon ether, macromolecule polymer and organic nitric acid ester is developed to overcome the problems of phase separation and low cetane number in the application of diesohol. The titration experiments prove that the mutual solubility be-tween the diesel and the ethanol is improved by adding 1%～2% (in volume) of this additive. The engine bench tests show that the cold starting performance of the diesohol with the addi-tive can be almost as good as that of the pure diesel. The effects which the pure diesel and several kinds of diesohol with differ-ent ethanol blend ratios have on the fuel economy, soot and the emissions of THC, CO and Nox are also investigated. As a re-sult, the specific fuel consumption of each diesohol is more than that of diesel, but the brake thermal efficiency and the soot intensity are all better than those of diesel. The Nox emission deteriorates with the increasing of engine load but has a decline trend under high load operation conditions with the increasing of ethanol blend ratio.

Key words: Cetane number improver, Diesohol, Emission characteristics, Phase separation, Solubilizer