Efficient operation of induction motor starter/alternator systems is an important part of the power-management function that is required in the self-contained vehicular environment. However, the nonlinear dynamics of the induction motor [1], parameter sensitivity to environmental factors, load complexities, and vehicular performance requirements make it difficult to determine and sustain the most efficient operating points. This article characterizes the performance of a fuzzy-logic controller for a hybrid electric vehicle (HEV) starter/generator (S/G) that is used to maintain optimum efficiency operation under both steady state and dynamic loading conditions. In steady-state conditions, automatic mapping of the maximum-efficiency operating points is achieved. Based on this data, the maximum possible efficiency under dynamic load profiling can be determined. In-vehicle dynamic loading is then emulated in the laboratory using a motor-development platform that can replay industry standard FTP75 road profiles and apply them to the S/G. The effects of velocity transients and the bandwidth of the fuzzy controller on efficiency are presented.