Biodiesel is being studied as one of the main diesel substitutes. Consequently, this study intended to examine the aspects of combustion performance and emissions of biodiesel fuels made from corn oil relative to the diesel fuel in an experimental boiler. The thermal capacity, T-c, and exhaust temperature, T-exh, as well as the common pollutants and emissions were tested over a wide range of fuel pressure ranging from 100 to 260 psi. All tests were conducted at the same level of input air for the fuels.