The importance of nano additives in biodiesel diesel fueled CI engine is discussed in this book, as well as the preparation of nano fluids, characterization, stability, and techniques for enhancing nanofluid stability. Thermophysical, combustion, and evaporation characteristics of nano fluids or biodiesel emulsified fuels are discussed, as well as corrosion in engine components, the influence of nano additives on engine performance, emission characteristics, toxicity of using nano additives, limitations, and various applications of nano particles.