It’s the age old dilemma facing a person who rents a car– should you buy the rental agency’s auto insurance coverage or will your credit card provide the extra insurance protection you need?

If you’re like most people who occasionally rent a car for personal use – including vacations or to temporarily replace a car in the shop – that answer requires some research.

Unfortunately, your credit card may not offer as much protection as people think.

Most major credit card companies – American Express, Discover, MasterCard and Visa – offer some rental car insurance protection but not all of their products do. That’s why reading the fine print and understanding coverage stipulations is essential for any consumer. For instance, MasterCard only offers protection on MasterCard World Cards, according to MarketWatch, and all credit cards have limits, caps, and exclusions. Not knowing these details could put a driver at financial risk in case of a serious crash involving heavy repair costs or personal injury.

Typically, credit cards provide only secondary insurance covering damage and theft - referred to as a Collision damage waiver (CDW) or loss damage waiver (LDW). This means the driver (or their personal insurance company) may be responsible for personal injury or liability costs, according to creditcards.com. This could turn your $30 a day car rental into a very costly event, especially if someone is hurt in a crash. Secondary insurance covers a driver up to the point that a personal auto insurance policy stops. This can be helpful if you have a high deductible on your personal auto insurance policy.

Experts recommend that you spend some time researching your coverage levels, speaking to your agent, and asking your credit card company so you fully understand coverage details. Here are some tips to consider when using a credit card to rent a car.

Consider shopping for credit cards with primary coverage. Because most credit card coverage is limited to secondary insurance only - consider signing up for a card that offers primary coverage. This means that your card temporarily replaces your insurance company in case of an accident involving a rental. What’s the benefit? A card with primary coverage means a fender bender doesn’t result in surcharges on your personal car insurance, creditcards.com reports. There may be an added cost for this service but remember that even primary coverage protection does not offer unlimited coverage.

Talk with your agent. Before renting a car, experts recommending calling one’s insurance agent to discuss how personal auto coverage may or may not extend to a rental vehicle. A personal policy may not adequately cover certain types of rental cars, such as sports cars or high-end vehicles, especially if it has a higher replacement value than one’s personal vehicle. Your insurance agent may advise temporarily boosting coverage levels when renting a car.

Research before traveling abroad. Credit card insurance and personal auto insurance coverage may not extend outside the U.S. and Canada, according to Esurance. In some cases, you may be forced to buy the rental agency’s insurance coverage.

Know exceptions and procedures. Both your credit card company and your insurance agent may have exceptions and require you follow certain steps. Failing to follow these procedures may render coverage null and void, according to Bankrate.com. For instance, collision damage may not be covered if due to reckless operation, drunken driving or even off-road driving. You may be declined coverage for a theft if you the doors were left unlocked. Also, when renting a vehicle, your credit card company may require that you refuse coverage offered by the rental car agency, adds NerdWallet.com. Even an accident on an unpaved or gravel road, or waiting too long to file a claim, may result in a coverage refusal, Nerdwallet says. Finally, if you’re using the rental car for business purposes, you may not be covered by either the credit card company or your personal insurance.

Ask about fees. Rental car agencies may charge “loss of use” fees if the rental car is damaged in an accident. This covers the agency for their loss of revenue while the car is repaired. Your credit card company may cover this – as long as the rental agency provides the “fleet utilization log,” according to creditcards.com. Unfortunately, many rental agencies consider these logs confidential and may not release them – leaving you to cover these fees.

Ronald Agrella is a freelance writer and the former editor of The Boston Globe’s Boston.com.