If you are concerned about the environmental impact at all, the impact on the planet of manufacturing a car is worse than the difference from improved gas mileage for several years, especially when you consider that the old clunkers that can't pass the emissions test (Yours are surely a long way from that problem!) have a tendency to be shipped to Mexico where there are fewer regulations. Maybe they will replace worse gas hogs down there - hard to say. The break even point would be way down the road. Aside from that, the car payments will offset any savings in gas mileage for quite a long time, depending on what you buy. The gas mileage simply doesn't justify the change. If people want new cars for other reasons, they need to be honest with themselves about their reasons. It isn't to save money and it isn't to save the environment.