Exception #2: Someone who's kid is driving an old clunker, and they take this opportunity to trade in the clunker, buy a new car, and hand down the parents current car to the kid.

In other words, it's aimed at me. In the long run though, it's not likely to be cost effective for me to trade in a 1987 Mercury Grand Marquis to buy even an efficient car like a Honda Civic, and pass down my 2001 Chevy Prizm (Corolla clone) to my son. While he's still in college, my son only puts 3000-4000 miles a year on his car, so the cost of fuel isn't that big a factor. The cost of repairs on the clunker is a factor, but it would never be a big enough factor to be worth spending $14,000 on a new car to eliminate.