In recent years, the use of oils and herbal products are considered as an alternative for diesel fuel. In addition to reducing the price of biodiesel produced from using herbal oils, which help to protect the environment. So far, the suitability of rapeseed, soybean and palm oil in direct injection diesel engine is evaluated. In the internal combustion engines, only approximately 1/3 of total fuel input energy is converted to useful work. Reduction of heat losses in different parts of the engine will lead to increased efficiency and useful work. The main aim of this research paper is to evaluate the effects of the biodiesel herbal fuel and nanocatalysts containing cerium oxide and molybdenum oxide on energy balance of a diesel engine using diesel-biodiesel-nanocatalyst fuel blends. The engine was run at the speeds of 2100 rpm and full load co