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An unmodified, direct-injected diesel engine was operated on diesel fuel and three blends of diesel fuel and sunflower oil. Heating of the fuels was used to change their viscosities. At normal fuel temperatures, specific fuel consumption and smoke emission increased for any power as sunflower oil content increased. Overall efficiency and exhaust temperature showed virtually no changes with fuel composition. Increasing fuel temperature caused a shift of best overall efficiency from high to low speeds, the magnitude of the shift depending on the plant oil concentration of the fuel. Thus fuel heating as a means of viscosity control may result in an efficiency penalty in the normal operating range of an engine. Typical plant oil induced engine contaminations such as wet stacking, excessive carbon accumulations, nozzle orifice blocking, and lubrication oil gelling were experienced.

Five T31 turbochargers used on a direct-injected diesel engine were tested as part of a plant fuel evaluation program. The engine was tested on the 200-hour durability cycle proposed by the Engine Manufacturer's Association (EMA). Part of the evaluation was an investigation of premature carbon and lacquer deposits, and wear within the turbocharger due to oil deterioration from the hybrid fuels. The lubricant viscosities for all tested fuels, except the microemulsion, were within normal limits. A sudden increase in lubricating oil viscosity for the microemulsion was observed. At the same time, higher blow-by and increased lubricating oil consumption was noted. All turbochargers displayed journal bearing wear but no rubs or unusual seal leakage was formed. The turbine shafts showed various degrees of hot shutdown and high temperature operation for different fuels. The turbine wheels and housings varied in color from a soft gray to dark black.