So says Clark Howard:
For 15 years, Clark has talked about the advantage of keeping a new car for at least 10 years or buying a used car and keeping it for at least four years. Cars lose about half of their value during the first three years, but then the loss ratio drops off pretty steeply after that time. Consumer Reports has now done a study on the virtues of keeping a car for 15 years. Bear in mind that most owners only keep their vehicles for three or maybe five years. But by keeping a car for 15 years or 225,000 miles, you save $31,000 dollars. The report found that during the course of 15 years, your average maintenance will be $18,000 and your insurance will be $18,000.