Engine energy-saving technology is the key direction of passenger car energy-saving. This paper has built energy-saving potential model, which could forecast the potential of engine energy-saving technology in 2015 and 2020 under such two constraints: overall target requirement of fuel consumption and curb weight range. Afterwards, the model was used to calculate energy-saving potential of narrow sense passenger cars (including basic car + SUV + MPV), which were equipped with single turbo charging technology, single GDI technology and the above two kinds of technologies integration. The research results will provide decision-making support for enterprises’ technology selection and product development.