According to a recent J.D. Power and Associates study, sales of certified used cars have increased 46 percent since 2000. What's a certified used car?

"Certified" used cars are sold by the original manufacturer, often with extended warranties that takes effect when the original warranty expires. They often operate just like a new car warranty covering a certain number of years or miles, which ever comes first. While these used cars with aftermarket warranties are sometimes advertised as "certified," they technically are not because the vehicle's manufacturer is not supporting the warranty in any way.

In many cases, a customer who purchases a certified used car will become eligible for benefits that a new car customer enjoys. This includes benefits such as service loan cars, shuttle pick-up and drop-off service, roadside assistance, free maintenance and low-rate "incentive" loans. Even if a specific perk is not part of the official certified program, you can sometimes negotiate additional features with your local dealer. Many certified programs will even offer longer warranties at an additional cost.

The real value is associated with the factory-provided warranty coverage that would be included in the purchase price of the car you're considering. Because some cars have a longer initial warranty when the car is purchased new, they then become a better candidate as a certified used car. In other situations, buying a certified used car will net the customer a longer warranty than if he or she bought that same car new. The attraction to certified used vehicles is clear - new car benefits at a used car price.

Many programs offer benefits not directly related to the vehicle itself such as trip routing, and trip interruption protection. Trip interruption protection is a feature that will reimburse the owner of a certified used car for incidental costs such as car rental, lodging, meals and out-of-town repair expenses.

The rules and dollar amounts vary from brand to brand, so check with your Auto Advisor for details about certified cars.