It's hard to beat it for convenience, but selling or trading your car at a dealership is a good way to lose out on $1,000 or more, says Melanie Kovach, senior director of private seller sales for AutoTrader.com, a website that hosts used-car classifieds.
"Generally, across all cars, it's about $1,000 to $2,000, but you can get more than that depending on what car you have," Kovach says.
Jack Nerad agrees. He's executive editorial director at Kelley Blue Book, a firm that specializes in setting values for used cars. Nerad says selling or trading to a dealer could net you up to 20 percent less than what you'd get in a private sale.
To get an idea of what the difference between a dealer price and a private sale price would be for your car, Kovach suggests logging on to a vehicle pricing site such as Kelley Blue Book, which lists prices for trade-ins and private sales.
Usually the gap between the two will be significant, because dealers make a big chunk of their profits by buying used cars at a lower wholesale price and reselling them on their lot at a higher retail price, she says.
If you sell your car yourself, "you can keep the profit that a dealer would be making if you traded your car in," says Kovach.