Using Unmodified Vegetable Oils as a Diesel Fuel Extender
100 Per Cent Vegetable Oil as Potential Fuel Sources 1/2
During World War II, Seddon (1942) experimented with using several different
vegetable oils in a Perkins P 6 diesel engine with great success. The results of this
experiment showed that vegetable oils could be used to power a vehicle under normal
operating conditions. However, it was noted that much more work was needed before
vegetable oils could be used as a reliable substitute for diesel fuel.
The Southwest Research Institute, Reid et al. (1982), evaluated the chemical and
physical properties of 14 vegetable oils. These injection studies pointed out that the oils
behave very differently from petroleum-based fuels. This change in behavior was
attributed to the vegetable oils’ high viscosity. Engine tests showed that carbon deposits
in the engine were reduced if the oil was heated prior to combustion. It was also noted
that carbon deposit levels differed for oils with similar viscosities, indicating that oil
composition was also an important factor.
Goering et al. (1981) studied the characteristic properties of eleven vegetable oils
to determine which oils would be best suited for use as an alternative fuel source. Of the
eleven oils tested, corn, rapeseed, sesame, cottonseed, and soybean oils had the most
favorable fuel properties.
Bruwer et al. (1980) studied the use of sunflower seed oil as a renewable energy
source. When operating tractors with 100% sunflower oil instead of diesel fuel, an 8%
power loss occurred after 1000 hours of operation. The power loss was corrected by
replacing the fuel injectors and injector pump. After 1300 hours of operation, the carbon
deposits in the engine were reported to be equivalent to an engine fueled with 100%
diesel except for the injector tips, which exhibited excessive carbon build-up.
Tahir et al. (1982) tested sunflower oil as a replacement for diesel fuel in
agricultural tractors. Sunflower oil viscosity was 14% higher than diesel fuel at 37°C.
Engine performance using the sunflower oil was similar to that of diesel fuel, but with
slight decrease in fuel economy. Oxidation of the sunflower oil left heavy gum and wax
deposits on test equipment, which could lead to engine failure.
Bacon et al. (1981) evaluated the use of several vegetable oils as potential fuel
sources. Initial engine performance tests using vegetable oils were found to be
acceptable, while noting that the use of these oils caused carbon build up in the
combustion chamber. Continuous running of a diesel engine at part-load and mid-speeds
was found to cause rapid carbon deposition rates on the injector tips. Short 2-hour tests
were used to visually compare the effects of using different vegetable oils in place of
diesel fuel. Although short-term engine test results were promising, Bacon
recommended long-term engine testing to determine the overall effects of using
vegetables oils as a fuel in diesel engines.
Schoedder (1981) used rapeseed oils as a diesel fuel replacement in Germany
with mixed results. Short-term engine tests indicated rapeseed oil had similar energy
outputs when compared to diesel fuel. Initial long-term engine tests showed that
difficulties arose in engine operation after 100 hours due to deposits on piston rings,
valves, and injectors. The investigators indicated that further long-term testing was
needed to determine if these difficulties could be adverted.
Auld et al. (1982) used rapeseed oil to study the effects of using an alternative
fuel in diesel engines. An analysis of the rapeseed oil showed a relationship between
viscosity and fatty acid chain length. Engine power and torque results using rapeseed oil
were similar to that of diesel fuel. Results of the short-term tests indicated further longterm
testing was needed to evaluate engine durability when rapeseed oil was used.