Raw oils generated by low-temperature coal pyrolysis were chemically characterized and subjected to tests in three diesel engines of different configuration. The coal liquids were tested as blends with conventional No. 2 diesel fuels, the coal liquids being 20-25% by volume. These tests were performed in support of a broader set of studies on the feasibility of using low-temperature pyrolysis to obtain liquid fuel materials from coal that do not require extensive, costly upgrading.Determination of physical and chemical properties of the pyrolysis liquids indicated a higher hydrogen/carbon ratio and lower aromaticity than typical SRC II and EDS middle distillates. Combustion tests were performed in both direct- and indirect-injection engines at three sites. The results were highly variable, the addition of the oil showing no effect on emissions and performance in some cases, reduced emissions on one engine, and increased emissions in other cases. The results are discussed with reference to prior related work.