Currently the number of automobile have been increased constantly and emissions emitted from automobiles are increasing gradually in terms of contribution of total amount of environmental air pollution. Accordingly the development of environmentally friendly eco-vehicles have been researched in many different research fields. Electric vehicle have been developed by Tesla and the market share is more then 80% and the key technology depanes on durability and acceleration of battery and motor. Environmentally friendly eco-vehicle using hydrogen, LPG, CNG and bio-fuel has modified and developed existing internal combustion engines. However, automobile engines to generate power have been used for 100 years after industrial revolution and there are a technical barrier in substituting internally combustible engine with electric vehicle and gasoline and diesel engine need to be developed to become environmentally friendly eco-vehicle by controlling exhaust emissions. In particular, diesel engine is better than gasoline engine in terms of thermal efficiency and engine power but more harmful particulate matter and NOx are emitted aggravate air pollution. This research aims to optimize fuel consumption by installing LNT system to a passenger diesel engine and then satisfy recent Euro-VI emission regulation..