Engine durability screening test of a diesel oil/soy oil/alcohol microemulsion fuel

A hybrid fuel and No. 2 diesel fuel were burned in direct‐injection diesel engines to compare the effects of the fuels on engine durability. The hybrid fuel was a microemulsion of soybean oil, diesel fuel, 190‐proof ethanol and 1‐butanol. The engines were run for 200 hr on each fuel with loads and speeds controlled by computer according to a cycle suggested by the EMA (Engine Manufacturer's Association). Engines were disassembled before and after the runs to determine the difference in wear and carbon deposits. The engine running on the hybrid fuel completed the 200‐hr EMA test without difficulty. The hybrid produced less engine wear than diesel fuel, but produced greater deposits of carbon and lacquer on the injector tips, intake valves and tops of the cylinder liners. Also, engine performance was degraded ca. 5% at the end of the 200‐hr test.