While the longer lifespan of small automobiles in recent years cancels out the reduction in CO₂ emissions from improved fuel efficiency, it contributes to reducing life-cycle CO₂ emissions by cutting CO₂ emissions at the time of vehicle manufacture. Given the current trend of improving fuel efficiency, the recent increase in lifespan is reasonable from the perspective of reducing CO₂ emissions. This suggests that drivers should replace their cars with more fuel-efficient cars such as hybrid or electric vehicles and use them as long as possible in order to reduce CO₂ emissions. Since driving distance has a positive correlation with fuel efficiency, purchasing fuelefficient cars creates a rebound effect in terms of increased CO₂ emissions due to greater driving distance. The vehicle choice model reveals that consumer preference towards fuel efficiency has gradually decreased as the weighting of fuel efficiency in the utility function has fallen over time. Evaluation of CO₂ emissions in the manufacturing process, suppression of growth in driving distance arising from increasingly fuel-efficient cars, and consideration for changing consumer preferences should be incorporated to facilitate future policymaking.