**4. Conclusions**

Biodiesel fuel was produced from four different oil feed stocks: waste cooking oil Coyote Jacks, waste cooking oil JC Alexander, and not used peanut and coconut oils. Biodiesel fuel blends (B5, B10, B15 and B20) for each oil feed stock were prepared by mixing the biodiesel fuel with Petroleum Diesel. The biodiesel fuel blends were tested on the Diesel Engine and the results were compared to those obtained with Petroleum Diesel Fuel. The results obtained with the four oil feed stocks show the same trends. The hydrocarbons HC and CO emissions decreased by increasing the amount of biodiesel blended with Petroleum Diesel. The HC and CO emissions decreased respectively by 20 % and 12 % for the B20 compared to the Petroleum Diesel while the NOx emissions increased by 2% and the change of the engine power was negligible (<2%).
