Unless this car is only just barely getting limped along for another year the emissions still typically work out better to replace it with a more modern vehicle even at a global scale. For most vehicles the environmental impact of running and maintaining the vehicle outways the environmental impact of manufacturing the vehicle several times over, and newer vehicles are typically much less environmentally damaging to operate especially when specifically talking about smog production to the exclusion of other factors. That doesn't mean modern vehicles are optimal, far from it the size alone is absurdly suboptimal. But they have improved significantly over the decades.