Slurry fuels of various forms of solids in diesel fuel were developed and evaluated for their relative potential as fuel for diesel engines. Thirteen test fuels with different solids concentrations were formulated using eight different materials.The injection and atomization characteristics (transient diesel sprays) of the test fuels were examined in a spray bomb in which a nitrogen atmosphere was maintained at high pressure and temperature, 4.2 MPa and 480°C, respectively. The diagnostics of the sprays included high-speed movies and high-resolution still photographs.The slurries were also tested in a single-cylinder CLR engine in both direct-injection and prechamber configurations. The data included the normal performance parameters as well as heat release rates and emissions. In most cases, the slurries performed very much like the baseline fuel. The combustion data indicated that a large fraction (90 percent or more) of the solids were burning in the engine. It appears that the prechamber engine configuration is more tolerant of the slurries than the direct-injection configuration.