Vegetable oils provide diesel engine performance similar to that obtained with diesel fuel, and this has been documented in many prior publications. Because they are potentially interchangeable with diesel fuel, interest has focused on vegetable oils as short-range alternate fuels. However, engine durability when burning vegetable oils may be adversely affected depending on the type of combustion system employed. Laboratory and field experimental tests have identified the prechamber engine as having the greatest short-range potential for using vegetable oil fuels. Performance and durability at low engine ratings are essentially the same as expected for operation on diesel fuel. However, at high engine ratings piston ring and cylinder liner wear are greater than expected for operation on diesel fuel. A laboratory program was successfully completed which resulted in a combustion system that would allow the higher rated prechamber engines to achieve normal life when burning 100% soybean oil. Fluid model tests utilizing high speed photography, single-cylinder engine tests utilizing fuel tracers, and a 200-hour multicylinder durability test were included. Extended endurance tests and experience with other vegetable oils are still required.