Certified used cars and trucks are supposed to undergo rigorous inspection and testing by a dealership's mechanics to make sure they're in top working order.

They typically suffer from less wear-and-tear and fewer cosmetic problems than the average used vehicle of that model and age, and come with some type of warranty.

Of course you'll pay more for a certified used car or truck -- an average of $1,680 more according to J.D. Power and Associates, a California-based market research firm. And there's no reliable data that prove certified used cars are dramatically more reliable than non-certified used cars.

But if you're nervous about buying used, choosing one that's been inspected and guaranteed in some way certainly reduces the likelihood you'll make a costly mistake.

The best certification programs are offered by the car or truck's manufacturer. They ensure vehicles are adequately inspected and repaired to meet their standards. Warranties issued through a manufacturer's certification program are honored at any of its dealers nationwide.

To get a manufacturer-certified car or truck you must buy it from one of its new car dealers. In other words, a used Lexus will only be certified through the Lexus program if it's purchased from a Lexus dealer.

In addition to that, many dealers have their own certification programs.

They're usually offered to used car customers buying a brand the new car dealer doesn't carry. A Chevrolet dealer, for example, might inspect and offer a warranty on a Dodge or Ford.

But you can't be sure that dealer-certified models are inspected and repaired as thoroughly as the manufacturers require and the warranty is only good at that dealer.

Be especially wary if the car or truck you're considering is certified by the dealer even though the dealership sells that brand. It often means the car or truck you're looking at couldn't pass the more stringent inspection required by the manufacturer -- or couldn't pass the inspection without repairs the dealer wasn't willing to make.

If, for example, you're buying a used BMW from a BMW dealer expect that car to be certified under the BMW program. That means you have to ask who's certifying the vehicle, the dealer or the manufacturer. Don't assume it's the manufacturer.

Finally, don't take any "certified" program at a used-car lot seriously. It's a marketing gimmick.

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