The fuel economy and emission advantages of diesel-electric hybrid powertrain modifications and an auxiliary fuel cell subsystem over those of a conventional midsize crossover SUV are discussed. The vehicle architecture is representative of one selected for the multiyear ChallengeX intercollegiate student design contest. To analyze the fuel economy, a simple “top-level” approach is used to estimate the fuel economy characteristics and performance potential to illustrate the advantages of the hybrid-electric powertrain configuration and the auxiliary fuel cells. Chained energy efficiency assumptions for the powertrain components lead to gasoline equivalent fuel mileage estimates. In the emission analysis, the greenhouse gases, regulated emissions, and energy use in transportation model is used to track the environmental impact of the powertrain on a well-to-wheels basis.