Diesel engines are one of the major contributors to the emissions such as hydrocarbons, particulates, nitrogen oxides, and sulphur oxides. Thus wide use of diesel engines leads to harmful threat of nitrogen oxide and hydrocarbon emissions. Improvement in the performance of diesel engines is an important challenge to be addressed, in the current era due to the fast depletion of fossil fuel resources as well as due to the harmful hydrocarbon and nitrogen oxide emissions. Due to stringent emission regulations worldwide, many investigations are carried out to minimize the above emissions by three methods viz. formulating new fuels, modifying engine design and exhaust gas treatments. The effects of nano additive and Reformed Exhaust Gas Recirculation (REGR) with diesel to find out the maximum possibility to increase the thermal efficiency as well as to reduce emissions from a compression ignition engine. A series of experiments were conducted to examine the combustion, performance and emission level of the diesel engine, using diesel fuel without and with different proportions of the nano additives.