It's summertime, and peak season forvacationers and car rentals. Even though most standard autoinsurance policies cover rental cars, roughly 20% of consumersalways purchase supplemental coverage when renting a car, and 20%do occasionally, according to a study by Progressive. Why? A studyby the National Assn. of Insurance Comissioners finds that 62% ofconsumers don't think their personal auto insurance automaticallycovers rentals, and 24% aren't sure whether their credit cardsprovide any coverage.

Most credit card companies offer somesort of free rental car collision coverage, along with other perks.But what exactly does it cover? A recent report by CardHub examines each major card network's rental car insurancepolicy and explains what type of rental car insurance coverageconsumers automatically receive through their credit cards, howthey can take advantage of it, which credit cards offer the bestinsurance coverage, and whether any other forms of supplementalinsurance are needed.

CardHub reviewed the publicly availableonline car rental policies of VISA, Discover, Mastercard andAmerican Express to answer: 1) Who is eligible for car rentalinsurance coverage?; 2) What vehicles are excluded?; 3) Whatexclusions do the policies have?; 4) What is the quality of thecoverage?; 5) How does one activate the benefit?; 6) How shouldclaims be filed?; and 7) How easy it is to obtain completeinformation about the policy?

Read on for the key findings.

1. All four major card networksprovide some form of rental car insurance coverage.

2. MasterCard is the onlynetwork that does not provide coverage on all of itscards.

3. American Express received thehighest cumulative score (90%) for its rental car insurance policy,while Discover ranked second (88%), MasterCard ranked third (79%)and Visa ranked last (74%).

4. All four major networksrequire cardholders to charge their entire rental car purchase ontheir credit card and decline supplemental insurance/CollisionDamage Waivers (CDW) offered by the rental company in order to beeligible.

5. None of the four majornetworks provides coverage for the rental of: 1) exotic, expensive,or antique cars; 2) trucks; 3) vehicles with open beds; or 4)off-road vehicles.

6. VISA is the only network thatdoes not cover accidents occurring on dirt and gravel roads.MasterCard only covers accidents on dirt and gravel roads if theyare “regularly maintained.”

7. All card networks excluderentals that exceed specified time limits, and a lot of cards comewith country limitations as well.

8. American Express is the onlynetwork not to provide coverage for renting certain popular SUVs –including the Suburban and Tahoe from Chevrolet, GMC Yukon, FordExpedition, Lincoln Navigator, Toyota Land Cruiser, Lexus LX450,Range Rover, and full-sized Ford Bronco.

CardHub recommended the following tips forconsumers weighing car rental insurance:

• Contact your insurance agent or carrier and find out ifrentals are covered under your standard policy. Older policies maynot offer this coverage.
• Ask your credit card issuer what limitations apply to thecar rental coverage they provide.
• Long-term rentals might not be covered by your existing autoinsurance, as time limitations may be imposed by your policy.
• Even if your personal auto policy covers rentals, it might notapply for rentals used for business travel.
• Rent a car of similar value to your own car to increase thelikelihood that your existing coverage is adequate for the rentalcar.
• If your existing policy does not offer coverage for aparticular type of rental car, ask about adding aninsurance rider for a small fee.
• If you are not a car owner but drive from time totime, consider purchasing a non-owner auto insurancepolicy.