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

Most credit card companies offer some sort 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 insurance policy and explains what type of rental car insurance coverage consumers automatically receive through their credit cards, how they can take advantage of it, which credit cards offer the best insurance coverage, and whether any other forms of supplemental insurance are needed.

CardHub reviewed the publicly available online car rental policies of VISA, Discover, Mastercard and American Express to answer: 1) Who is eligible for car rental insurance coverage?; 2) What vehicles are excluded?; 3) What exclusions do the policies have?; 4) What is the quality of the coverage?; 5) How does one activate the benefit?; 6) How should claims be filed?; and 7) How easy it is to obtain complete information about the policy?