The performance, combustion, and emissions of three coal-derived, test fuels were compared to a Phillips D-2 control fuel in a single cylinder, direct-injected, Diesel engine. The three synthetic test fuels were formed by varying the degree of hydrotreatment of a coal-liquid produced from the Exxon Donor Solvent (EDS) process; the three fuels have Cetane numbers of 29, 34.2, and 38.2.The objective of this research was to examine the effect of the degree of hydrotreatment on combustion, performance, and emission characteristics. The emissions measurements included both gas-phase emissions (CO, NOx, unburned hydrocarbons, and aldehydes), and particulate emissions. In addition, the Ames test was used to analyze the mutagenic activity of the soluble organic compounds found in the exhaust particulate.The results of this study show that as hydrotreating is increased, fuel economy and thermal efficiency increase, premixed fraction and peak mass burning rate decrease, emissions of NOx, CO, and aldehydes decrease, and, for most conditions, particulates decreased. Also, the mutagenic activity of the soluble particulate decreased with increasing the hydrotreatment severity.