En español  |  Last March, Robert Jones went to Mac Churchill Acura in Fort Worth, Texas. He didn't need a new car; he was just redeeming a free-gift notice received in the mail. But five hours later, Jones, then 83, traded in his Ford Explorer for a 2009 Acura MDX. The dealership charged him $48,000 — thousands more than most MDXs sold for new. The book value of that model? Low 30s. After Jones' daughter, Jan Duran, found out, she met with Mac Churchill. "I explained that my father was recovering from a mild stroke," she says. But Churchill wouldn't roll back the deal. So, Duran returned the car to a different Acura dealer, to be resold at auction (likely at a big loss, which Jones would be responsible for paying), and wrote to On Your Side.

The Texas Department of Motor Vehicles, which oversees car sales in the state, says that inflating the price of a used vehicle isn't illegal. But, to my mind, Mac Churchill's huge markup tested the boundaries of ethics. So I asked the dealership to cancel the contract. Like his boss, general manager Sharbel Lattouf refused the request.

Know what that car is worth before the test-drive. — Jesse Lenz

Next stop: American Honda Motor Co., which oversees Acura franchises. Spokesman Gary Robinson was in a different gear. "We're sorry that happened," he said, "and we will make it right." Acura Financial Services reversed the agreement, and the Mac Churchill dealership sent Jones a check for his down payment and the fair market value of his trade-in.

A new or used automobile can be a risky impulse purchase: It pays to be prepared when buying a car.

Do your research

Know what that car is worth before the test-drive. Compare prices online, read reviews and research the history of the specific vehicle you're thinking of buying.

Don't buy their time line

Salespeople know that if you walk off the lot, you might never come back. That's why they say, "The deal is good only today." Ignore them. Take your time before signing.

Create some competition

Unless you're buying a Lamborghini, several nearby dealers are probably selling the same car. Get quotes from them, too.

Find your own loan

Credit unions can often beat dealer-originated deals. Get the financing first, so you can focus on features and price without being distracted by the dealer's financial sleight of hand.

Also of Interest

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• 10 toughest states for earning a living

Visit the AARP home page for great deals and savings tips