Depending on your preference for engaging in negotiation and buying and selling, there is a pretty reasonable model to show you should buy a typical 3 year old used car and then sell it around year 5 or so thus buying a car when it is still reliable has past the fastest part of its depreciation curve and selling it when it's about to fall down the reliability curve and still worth close to what you paid for it.
You save even more by buying at 3-4 years and keeping until 10 years or 150K miles. Cars today are remarkably reliable well past a 5 year mark. You'll have an occassional several hundred dollar repair. That's less than what most people pay every single month for their crazy car habit.
Plus, you only go through the aggravation of buying and dealing with your DMV 1/3 as often this way...
Try that with a Honda and you learn that 3 yr-old Hondas cost the same as new Hondas, because the depreciation is less than the overhead of reselling the car (through a dealership)
