Petroleum deposit derived from fossils that are non-renewable are running low, to reduce dependence on petroleum it is necessary to develop alternative renewable energy, namely by utilizing oils from plants to become biofuels such as biodiesel. Biodiesel is a renewable fuel made from vegetable oils or animal fats. Biodiesel is a fuel that is used as an alternative to fuel from diesel engines. In this research, the raw materials used are biodiesel from castor oil and biodiesel from corn oil, then the two oils are combined with diesel oil, the ratio is 5% biodiesel - 95% diesel, 10% biodiesel - 90% diesel, 15% biodiesel - 85% of diesel fuel is then given the code B5, B10, and B15. The goal of the research is to know the performance of diesel engines using100% high diesel oil and mixed biodiesel castor oil –biodiesel corn oil and high diesel oil variation with B5, B10, B15. The research starts with testing the physical properties of fuel includes viscosity, density, flashpoint, calorific value, test of diesel engines with diesel fuel of pure, testing diesel fuel with B5, B10, B15, and test the characteristics injection of 100% high diesel oil, testing the characteristics injection of the fuel B5, B10, B15, data processing, data analysis, and conclusion. The whole of these tests are done in the laboratory of mechanical engineering UMY and LPPT UGM Unit I. The research results it was found that overall pure solar fuel had much more power than fuels B5, B10, B15. But B10 fuel produces the greatest power at the maximum load of 1.493 kW or 1.42% above the pure diesel fuel. Specific fuel consumption (SFC) on biodiesel B5, B10, B15 and lower than of pure diesel fuel or more efficient in its fuel consumption. The injection characteristic test results show that biodiesel variation of B5 has the longest penetration spray of 608.24 mm at 0.08 seconds and has a spray angle of 10.54o , diesel fuel has a shorter spray penetration than B5 of 594, 42 mm, but has a greater penetration angle than B5 which is 10.57o . Whereas biodiesel variation of spray angles B10 10.44°, with long spray penetration of 606,71 mm. Then on biodiesel variation B15 has angle and length the smallest of the penetration of sprays the entire fuel variations with angle 10.15° and long spray 590,54 mm.