A relatively old car emits 4.35 tons of CO2. But speaking with sure accuracy, as an old car goes beyond five years, it radiates higher than 4.35. If it reaches ten years, it will produce 43 tons of CO2.
Bottom line: don't wait for your car to reach its lifespan. Try to be less consistent in following the maxim "make the most of it." This ideology certainly doesn't apply to your old cars.