A service contract tries to solve a narrow problem: a covered failure arrives as one large, unplanned invoice on a car you intend to keep. Before you accept that you have that problem, check whether something you already own or pay for carries part of the same risk. If it does, you may be paying twice for the same protection, or you may be buying a contract for a gap that was already partly closed.
Where the overlap usually hides
Start with the factory warranty in the owner's paperwork. Note how long it runs and whether it ends on age or on mileage. That line is usually where a contract's coverage starts to matter, so it is the first thing to compare.
Next, check the credit card you used for the purchase or for any repair. Some card issuers describe a benefit that extends a manufacturer warranty for purchases made on the card. Ask for the written benefit guide, not the marketing summary, and read what it excludes.
Then check your auto insurance and any employer benefit. Roadside assistance, rental cars after a breakdown, and repair referrals are common add-ons. Roadside help is a different promise from repair coverage, so do not count it as protection for a failed part.
Last, look for any protection you bought at a dealership or through a lender and then forgot. Those papers often sit in the glovebox folder with the title.
How to tell whether you have the problem
You likely have the problem when three things are true. The car is past its factory coverage at the age you plan to keep it. A large repair would strain your cash with no plan in place. And your household cannot easily do without the car.
If the overlap already covers most of the risk you are worried about, a contract may fill only a small leftover gap. Weigh that gap against the price in the contract's own paperwork, not against a number from a sales conversation.
What to write down before you sign
Make a short list of each existing source. For each one, note what it covers, what it excludes, how a claim starts, whether it ends on age or mileage, and whether it requires a particular shop or payment method. Then set that list next to the contract's coverage page and look for the gaps that remain.
Ask the seller, in writing, whether the contract overlaps with the factory warranty or a card benefit, and whether it reduces what those other sources would pay or runs alongside them. A clear written answer is worth more than a verbal one.
If a contract is offered, look for a posted sample contract before you rely on any summary. Providers that publish one are listed on our sample contract page. Read the sample against your list, and decide only about the gap that is left.