Are you missing thousands in credit card rewards?

Reading the fine print on credit card offers could save you substantial cash—and not just by avoiding fees. There are a lot of valuable perks listed in card terms that go unnoticed.

"There's a ton that consumers are missing out on," said Odysseas Papadimitriou, chief executive of comparison site CardHub.com.

Several cards offer good reason to save your receipts on big-ticket purchases. Citibank, Discover and MasterCard all offer price adjustments if the cost of an item falls shortly after you bought it, said Kevin Yuann, director of credit cards at comparison site NerdWallet.com. Discover, for example, will refund up to $500 per item if you find a lower price within 90 days. Not tough to do, especially heading into the holiday sale season.

Read MoreStrategies for a better credit score—fast

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Most cards also automatically double the manufacturer's warranty, adding up to another year of coverage. "That can eliminate the need to buy an extended warranty," Yuann said. Check the requirements when you buy: Some issuers require you to register the purchase, and you'll definitely need to hang on to the receipt.

Travel-related perks can also add up. "When you're making a purchase in that category, it's worthwhile to understand what coverage you get," said Papadimitriou. Some cards waive transaction fees (up to 4 percent) for making purchases in another currency; most offer some kind of car rental insurance, which might save as much as $25 per day. Cards from World MasterCard are among those offering coverage for lost or delayed baggage, reimbursing travelers up to $3,000.

Read MoreA common credit report surprise that will cost you

To take full advantage, check with two sources: Your issuer (say, Chase) and the card's network (Visa, MasterCard), Yuann said. Some perks are card-specific, while others apply more broadly to a bank or network's offerings.

—By CNBC's Kelli B. Grant

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