The primary problems associated with straight soybean oil as a fuel in a compression ignition engine are due to high fuel viscosity. Transesterification provides a significant reduction in viscosity, thereby enhancing the physical properties of the fuel to improve engine performance. Methyl, ethyl, and butyl esters of soybean oil revealed fuel properties similar to diesel fuel. Engine wear, deposits, performance, and emissions are reported for each of the ester fuel's and reference diesel fuel's 200-hour engine tests. Analysis of lubricating oil samples are also presented as well as complete fuel injection system test results.