Q: Do any credit cards still double the warranty on items bought on their cards?

A: Credit card issuers carry lots of clout with merchants and manufacturers, making warranty extension a common but underutilized benefit of many popular cards.

Lifehacker investigated this issue, and their findings match what we've heard from readers and from brand managers at all four of the major credit card payment platforms:

• American Express offers the most robust warranty protection, adding up to one year of protection to eligible purchases that carry a manufacturer's U.S. warranty of five years or less.
• Visa Signature cardholders enjoy automatic access to Visa Warranty Manager Service, a comprehensive plan that tracks large purchases and handles warranty claims for an extra year. Some partner banks extend this Signature perk to traditional Visa accounts, as well.
• MasterCard makes an extended warranty program available to its partner banks, who can enroll cardholders for an additional year of protection after the first year of a manufacturer's warranty.
• Discover offers no guaranteed warranty extension program, but enables cardholders to sign up for inexpensive supplemental warranties from SquareTrade on its website.

Most of the best credit cards featured at CardRatings.com offer some kind of warranty extension. Filing a claim and fixing your merchandise can require very different procedures from card to card:

• American Express leverages its relationships with merchants, who often handle customer claims at the original point of purchase. A merchant may elect to swap the broken merchandise for a "like new" equivalent, such as an open box return of the same model. If a manufacturer charges you for an authorized repair, American Express will reimburse your fee.
• Visa, MasterCard, and most third-party warranty extension programs require you to submit a claim to their program management team before you contact a manufacturer or a merchant. In most cases, you'll receive instructions to send your broken gear to the warranty company's central facility instead of to a manufacturer.

Regardless of your credit card, always start an extended warranty claim over the phone with your lender's customer service representative.