The U.S. Department of Defense faces growing fuel demand, resulting in increasing costs and compromised operational capability. In response to this issue, the Fuel Efficient Ground Vehicle Demonstrator (FED) program was initiated in order to demonstrate a tactical vehicle with significantly greater fuel efficiency than a Humvee while maintaining capability. This article provides an overview of a systems engineering methodology for maximizing fuel efficiency and its application in concept development for the FED program. Engineering tools and methods used include tradespace definition, provisional baseline product models, decomposition of energy expenditure over the product usage cycle, structured technology market surveys, complex systems modeling & simulation tools, and design space exploration / Pareto optimization. The methodology explores the impact of technology on fuel efficiency along with other aspects of vehicle development including drive cycle definition, operational requirements, subsystem specifications, and architecture.