The flywheel energy-storage unit is examined as a tool for engine load management. The control decision to store or retrieve energy is formulated and discussed. Vehicle dynamics are simulated on a digital computer in combination with dynamic programming techniques to obtain optimal operation policy. The simplified algorithm is explained, as well as the cost-function criteria and optimization constraints. The sensitivity of the optimal path and the vehicle gas-mileage improvements are elaborated. The study of losses indicates that the transmission is the largest energy sink in the power train. The result of this study provides an indication of the appropriate real-time control policy.