I don't think that's it. When buying a used car, one has to be aware of it's condition. And since we can't see the engine or transmission internals, we must pick up on clues that we can see to determine if a car is a good investment or not. A major clue is the previous owner. Would you rather buy a used car from a middle aged lawyer or a teenage male? It has been my experience - and probably the experience of others - that most teenage males do not take proper care of their vehicles. Because of this, I would not purchase a car that I know belonged to a teenage male.

Similarly, it's undesirable to purchase a car that has been consistently driven hard or on the track. One surefire signal that a car has been driven hard is the addition of mods. If someone is willing to spend $$$ on a custom exhaust to increase noise and maybe squeeze out an extra 10 HP, then it's reasonable to assume that the driver also revs the engine to the redline at every shift. No one in their right mind should buy a used car with that kind of red flag.