The technical feasibility of superefficient family cars has been demonstrated. Yet it has typically compromised vehicle performance, safety, cost, manufacturability, or marketability. Industry experimentation has tended to focus on improving performance, or on implementing hybrid-electric drivesystems in essentially conventional vehicles, or on reducing mass and drag, or on improving safety—but has rarely attempted to optimize all of these as a system. Maximizing benefits through synergies between platform, chassis-component, and drivesystem design parameters seems poorly understood. Whole-system engineering-design is essential to move toward commercial viability. Second-by-second simulations and performance modeling provide evidence for automobiles 3–4x more fuel-efficient than today’s, with emissions approximating the California Air Resource Board’s proposed Equivalent Zero Emission Vehicle requirement for hybrids, and with safety, performance, and marketability surpassing that of many current automobiles. The commercial success of such designs depends on the concurrent optimization of numerous parameters, with emphasis on tractive- and accessory-load reduction and on component and control optimization. Platform optimization, subject to appropriate design criteria, must precede or accompany new drivesystem technologies, because only tractive-load reduction makes hybrid drivesystems commercially viable. Thus the artful combination of hybrid-electric drive with lightweight, low-drag platform design appears requisite to the cost-effective optimization of efficiency, emissions, performance, and safety for production worthy and marketable automobiles.