<prompt> Human: What is the optimal age to purchase a car at, i.e., the age at which new car depreciation and the risk of serious maintenance issues is best balanced?  <response>: I buy my cars from autotrader.com, and this is the search I do: Mileage: up to 60,000 miles Age: up to six years old Brand: your choice, but I get FordsI always find what Im looking for -- a reliable car at a good price. I typically keep my cars until 150,000 miles. 