The automobile is one of the main means of transportation in urban areas and it is responsible for a large amount of environmental impacts. Much has been talked about the consequences brought by the automobile during its life time. In this study, it is evaluated the consumption of the energy during the life cycle of the material in an automobile considering the materials extraction, the products of the parts, the automobile assembling, the use of the automobile and the recycling of materials. The period of time of the use of the automobile is varied as well as the efficiency. The main purpose of developing this study is to analyse the importance of the stage of the use of the automobile in the whole life cycle of the material in terms of energy requirements. The results show the energy consumption for the different efficiencies and automobile exchanges. It is interesting to notice that the augmentation of the life of the automobile from nowadays average (150.000 km) brings advantages. This is true till a certain number of exchanges, when the energy consumption increases again due to the fixed part of equation 1. The optimum exchanges varies according to the efficiency considered. The main result shows that not always the better efficiency means environment improvement when the whole life cycle is being under consideration. © 1998 Society of Automotive Engineers, Inc. Guidelines for Life-Cycle Assessment: A code of "practice" (1993) Pub. SETAC. Workshop, , SETAC. Sesimbra, Portugal. Ed. Consoli, F. Et al. 31/3-3/4/1993Curran, M.A., (1996) Evironmental Life Cycle Assessment, , McGraw HillKeoleian, G.A., Kar, K., Manion, M.M., Bulkley, J.W., (1997) Industrial Ecology of the Automobile: A Life Cycle Perspective, p. 159. , SAEGraedel, T.E., Allenby, B.R., (1998) Industrial Ecology and the Automobile, p. 243. , Prentice Hall IncWICE (World Industry Council for the Environment) (1994) Report, p. 16. , Life Cycle Assessment: an environmental management tool. OctFussler, C.R., Krummenacher, B., Ecobalances: A key to better enviromental material choices in automobile design (1991) Material Design, 12 (3), pp. 123-128. , JunDanholt In Bragg, G., Materials: A key to 100 years of automobile progress (1996) Auotomotive Engineering, 104 (12), pp. 93-99. , SAE. DecEmmenegger, R., Daehler, J., Riedwyl, P., (1989), Entwicklung des durchschnittlichen Benzinverbrauchs der TCS Testfahrzeuge 1974 bis 1988. Technisches Zentrum TCS. Jan