Maintaining the current ratio between certified and the customer-observed fuel consumption even with future required levels poses a considerable challenge. Increasing the efficiency of the driveline enables certified fuel consumption down to a feasible level in the order of 80 g CO₂/km using fossil fuels. Mainly affecting off-cycle fuel consumption, energy amounts used to create good interior climate as well as energy-consuming options and features threaten to further increase. Progressing urbanization will lead to decreasing average vehicle speeds and driving distances. Highly efficient powertrains come with decreased amounts of waste energy traditionally used for interior climate conditioning, thus making necessary a change of auxiliary systems. The recent rapid success in lowering the certified fuel consumption following the announcement of coming regulations is according to introduction of readily available technology and re-balancing of attributes using existing industrialized concepts. Cost of ownership and market are not sufficient drivers in the medium term to overcome the increased cost for the most fuel efficient technology. In this paper, the current starting position for the transition to highly energy-efficient vehicles is analyzed in a generic logical frame of analysis. An overview of different driving cycles is given. Mid- and long-term technical solutions for achieving the indicated legal requirements, as well as possible paths of transitional design and concept changes are discussed, as well as related engineering and research challenges.