This paper presents Exxon Enterprises Inc.'s approach to the economic evaluation of advanced automotive power systems. The paper derives and compares projected initial costs and operating costs for a subcompact car and a full size car powered by four different advanced power systems, i.e. an advanced spark ignition engine, a lightweight diesel engine, a battery powered motor, and a diesel electric hybrid system.The operating economics are based on a detailed analysis of the power system energy consumption. A proprietary computer program was used to simulate vehicle operation on a specific driving cycle and thus provide suitable energy consumption estimates. The initial and operating costs of the vehicles also reflect the different size and weight of the power systems, as well as weight propagation effects on the rest of the vehicle. For a meaningful comparison basis, each vehicle power system is sized to achieve an equivalent performance level (carrying capacity, acceleration capability, etc.), to the extent possible with motive components of vastly different characteristics.