Keeping an old car functioning is only better for the environment up to a certain point. If your cars are staying on the road long enough, eventually it makes m

Keeping an old car functioning is only better for the environment up to a certain point. If your cars are staying on the road long enough, eventually it makes more environmental sense to replace a 50 year old car that gets 18 miles per gallon with a new one that gets 45 and can last another 50 years.