Enterprise Car Rental Coupons 20% OFF: Get 20% off checkout at Enterprise.com. Save up to 50% when you rent a car from Enterprise! 

 In 2015, indu stry estimates put the annual revenue of U.S. car rental companies at more than $24 billion, with 1.857 million cars at 18,293 rental locations. With so many folks renting cars so frequently, you would think the process would be straightforward and transparent -- yet somehow it is anything but.

Do I need to buy additional insurance? If not, am I exposed at all? What about paying to refuel the car? I hear horror stories about phony damage claims; should I be worried? No one is around to inspect the car with me; should I  be worried? Can I drive to Mexico? What about all the other stuff they offer me at the rental counter? These questions come up pretty much every time we rent a car. Again, anything but straightforward. 

1. Prepaying for gasoline.

Prepaid gasoline charges appeal to our desire for simplicity while traveling, and also to concerns about being late for flights, as every few minutes added to the trip to the airport create more risk for arriving too late to board. As airport security has added considerable time to this process, rental companies have come up with new options for car refueling, and are giving them the hard sell at the rental desk.

2. Failing to check on your way out for a place to refuel on your way back.

The best time to find a place to refuel your vehicle is immediately after you pick it up. As you are driving away from the airport or rental agency, take note of the local gas stations, and make a plan to return to the most easily accessible or best-priced of them at the end of your rental. The road and neighborhoods around airports can be confusing and unfamiliar, so you don't want to be driving in circles looking for a gas station as your flight time approaches. Figure this out on your way out, when you are not pressed for time.

3. Purchasing insurance, reason No. 1: your own auto insurance covers you.

Before accepting this one at face value, it should be emphasized that auto insurance policies can vary considerably, so you will want to check with your own insurer directly. If you have the minimum legally permissible coverage, it may not include coverage for rental cars -- whereas if you have what companies call "full coverage," it almost certainly does. Call or email your insurer to find out.

4. Purchasing insurance, reason No. 2: your credit card covers the rest.

Anything your own car insurance does not cover, it is likely that your credit card will. In some cases the credit card coverage is as good as or better than your auto insurance; in others it is intended to be secondary insurance to help cover anything your auto insurance does not.

5. Ignoring one possible caveat: "loss of use" insurance.

car rental contractA new-ish fee applied by car rental companies in the event of a damaged vehicle is "loss of use" charges, which are applied for the potential revenue lost when one of their cars is off the road during a repair. This is typically charged in the amount of a day's rental for that vehicle, and most auto insurance companies do not cover this fee. Many credit cards do, however, as shown in the link above; American Express, Mastercard and Visa all offer "loss of use" coverage with rentals paid for with most of their cards.

6. Ignoring potential offers for upgrades.

In the past, I've recommended reserving a low-priced car and then inquiring about upgrades at the rental desk. This works best at busy times when the garage is running low on lower-priced cars, and may offer you free or very affordable upgrades to a larger car class due to inventory management issues.

7. Failing to check for AAA, AARP, reward program or other discounts.

Many membership programs establish relationships with car rental companies as a member perk. These include travel organizations like AAA, airline frequent flier programs, age-specific organizations like the AARP, and even some sports- or hobby-focused groups. Rental car discounts are typically listed on the organization's website; you are already paying membership dues, so have a look before booking and you could find a great deal.

8. Making too cursory an inspection upon departure.

When you pick up your car, check it inside and out for anything that could potentially be considered damage before you drive away. Look for scratches, scuffs, loose parts, working power windows and mirrors, and more.

9. Leaving final inspection to chance.

Recently, the procedure of returning cars has come to resemble checking out of a hotel, where you leave your keycard on the night table and head out the lobby door with only a wave to the front desk -- no more official checkout, key return or interaction of any kind needed. Car rental returns have taken on a similar feel; as often as not, you follow signs to the back of a row of recently returned cars, take out your stuff, leave the key in the car and walk away without ever speaking to anyone directly.

10. Crossing international borders.

Most U.S. car rental agreements do not allow you to drive the car across international borders (which means to Mexico or Canada for domestic rentals). Additionally, your U.S. car insurance rarely covers international car rentals, so you will likely want to purchase insurance from the rental company at the time of rental.

Stateside, typically rental counters located near the borders either display or explain this policy clearly -- if you rent a car in Nebraska, they might not mention it, of course -- but you want to be aware of this yourself. If you do drive across international borders and you have a problem, most of the protections of your rental contract, insurance and other sources may be negated.