7 rental car mistakes that could cost you hundreds of dollars, according to experts

Renting a car can add more flexibility to your trip. Sometimes, it's the whole point of the vacation. (Hello, road trip!) And other times, it's a cost-saving choice to avoid expensive rideshares and taxis.

But while rental cars can save you money, mistakes do happen. They can not only put a damper on your trip, but also cost you hundreds or even thousands of dollars. 

Yahoo Travel spoke to experts who can help you avoid these costly pitfalls. Here's what you need to know before you get behind the wheel of your rental car, so you can ride off into the sunset with peace of mind. 

1. You didn't track the price 

Most people assume that whatever price they are initially quoted on a travel website is the price they have to pay, says Jonathan Weinberg, founder of AutoSlash , a website that helps travelers find rental car deals and tracks prices after they book. But that's not necessarily the case, as rental car pricing often fluctuates multiple times a day, he says. 

"The reality is that people who track their rates, whether they do it on their own or they use a service like AutoSlash, end up saving about 20% over people who don't track their rates. So it can be a significant savings," Weinberg tells Yahoo Travel. 

Sally French, NerdWallet travel expert and cohost of the Smart Travel Podcast, tells Yahoo Travel that's why you should always book a refundable rate.  

"Most rental car companies allow you to make a reservation to lock in a rate now, but don't require payment until you get to the counter," she says. While you should lock in a rate in case prices rise, which happens, you should always check back to see if your price dropped instead. That way, she says, "you can make a new reservation at the lower rate, and cancel your old reservation."

Check the cancellation terms before booking, as prepaid reservations may carry cancellation fees. Reservations made through third-party websites may also have different rules.

2. You didn't get proper insurance 

Without insurance, a minor scrape can turn into an extremely expensive situation. That's why it's crucial to check whether you're covered before you get to the counter, either by your personal auto insurance policy or built-in coverage with the credit card you're using. 

Stacey King, associate travel adviser at AAA Northeast, tells Yahoo Travel that you should check your specific policy, even if your personal auto insurance carrier covers rental car use. Specifically, King says to look into "loss of use" coverage, meaning coverage for charges the rental company may impose while a rental vehicle is damaged and must be removed from the rental car service for repairs.

"In some cases, the rental company may seek reimbursement for the time the vehicle cannot be rented to other customers, and not all personal insurance policies cover that expense," she explains. 

Either way, read the fine print and make sure your rental car booking meets your policy's requirements.

3. You left a mess in your rental car  

Michelle Couch-Friedman, founder of Consumer Rescue , a consumer advocacy website and organization, tells Yahoo Travel that people who are in a hurry to return their rental car sometimes forget to take everything out and end up paying excessive cleaning fees, even if the mess doesn't seem all that big. 

Take everything out of the rental car to avoid additional charges. Better yet, she says, make sure you vacuum the car before you return it. The rental car company could charge you for those cookie crumbs from road trip snacks or sand from the beach.

4. You didn't document your car's condition at pickup

You want to make sure you return your car in the same condition it was in when you picked it up (allowing for normal wear and tear), and you certainly don't want to be responsible for a dent on the bumper that was there before you drove away.

"When picking up the vehicle, it's critical to conduct a thorough inspection for scratches, dents, chips or any other existing damage," King says, recommending that travelers also take photos or videos from multiple angles before leaving the lot. "If anything is found that is not already documented, notify the rental agent immediately and make sure it is noted on the rental agreement."

Since images and videos of the car are date- and time-stamped, King says, "they can serve as valuable documentation if questions arise later about when damage occurred."

French also suggests dropping off the car when an employee is present so they can conduct a final walkthrough and hand you a receipt in person. If you notice any discrepancies between what's on your bill and your documentation of the car's condition, you can dispute the charges with an employee face-to-face and share your evidence.

5. You didn't save your receipts (or the mileage)

Weinberg also recommends snapping a photo of the dashboard when you return the car. "It shows the fuel level, it shows the mileage and, if you filled up the tank, then you have a gas receipt proving that you returned the car full," he says.

"We get stories every single day from customers where they say, 'I returned the car full. I was charged $50 for gas. How do I claim credit for this?' And I'm like, 'Well, do you have any proof that you filled the car up?' 'No, I didn't take any pictures. I threw the receipt away,' that sort of thing," he continues.

"So, that's a big mistake that can easily be avoided by just taking a picture at the end of the rental."

6. You prepaid for gas

Rental car companies typically give you the option to prepay for a full tank of gas, so you don't have to worry about refilling it before returning the car.

But Weinberg says that choosing prepaid gas often ends up costing you. Since you're prepaying for a full tank of gas, any gas left in the tank when you return the car to the lot will essentially be "a gift" to the rental car company.

"The only time I would say that prepaid gas might be worthwhile is if you have a very early morning flight and you're worried about not being able to find the gas station close to the airport," he says. "But for all others, I would say that it works out better financially if you fill up the tank yourself and don't prepay."

7. You returned the car to the wrong location

Many car rental companies, especially at airports, have return lots that are very close together — and if you are returning a car without checking in with an employee, it's possible you could accidentally return it to the wrong place, Couch-Friedman says.

"Many people put the key on the dashboard and walk away, and that's the end of it. But if you return it to the wrong location, you're in for a big surprise later because sometimes those cars will sit for weeks before someone notices … and then you're on the hook for all the days that the car wasn't in the inventory," Couch-Friedman explains. 

To avoid this mistake, Couch-Friedman says to "get a receipt" from an employee you've confirmed works for the company you rented from. (Consumer Rescue has documented a case in which an employee at the wrong company accepted a rental car .) That way, "if they send you a letter sometime later that the car is missing, you have proof that you returned it," she notes. 

King says that when you're getting the receipt, you should also "review the rental agreement and confirm that the pickup and return dates, times, locations and pricing match what was originally booked." Taking this extra time, she says, can "help prevent billing disputes later."