The effect of changing economic conditions on quality requirements of commercial vehicles is discussed. Special attention is given to reliability and longevity aspects. To facilitate the evaluation of changes of reliability on total life costs of automobiles, a mathematical model was developed, which contains also seperate variables defining the energy and material content in the life cost structure. The concept of optimal longevity is analysed and factors influencing it are considered. It is shown, that improvements in automobile reliability can lead to considerable savings of energy and material.