Please don’t do what Richard Rubin did to his rental car this summer.

When he picked up his midsize sedan from Enterprise in Granada, Spain, an agent showed him that the fuel tank cover was spring-operated and said the car took gasoline. But when Rubin found that the vehicle wasn’t big enough to fit three passengers in the back seat as described on Enterprise’s website, he asked for a minivan.

“The agent tapped on the fuel tank cover again to show me how to open it and told me it used gasoline,” says Rubin, an editor from New York City.

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Something must have gotten lost in translation. When he filled the tank with gasoline a few days later, the engine sputtered to a stop. It turned out that the minivan only took diesel. Enterprise towed the van to a nearby mechanic for repairs. Rubin and his group paid 90 euros ($90) for a taxi ride to Granada.

The next day, while touring Granada’s historical Alhambra palace complex, Enterprise called Rubin with some bad news: He needed to pay 1,500 euros for repairs, because misfueling a car constitutes negligence and is not covered by the company’s damage insurance. The company later reduced his bill to 844 euros, including 100 euros for an “administrative fee” and 115 euros for a “loss of use” fee. Rubin says he has no recollection of any warnings to only use diesel in the vehicle.

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Misfueling is one of the most common mistakes travelers make, particularly when traveling abroad. Yet a gas mix-up is entirely avoidable. Vehicles often have warnings next to the tank that say “diesel fuel only,” although they may not be in English, and the fuel nozzles at some service stations will prevent you from using the wrong gas. But never take someone’s word for it.

I asked Enterprise about Rubin’s case. A representative promised to review his bill, but added that his experience offered a valuable lesson for other customers.

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“Take the time to know the vehicle you are renting,” spokesperson Lisa Martini told me. “Learn how to operate essential functions, like where the seat levers are located and how to operate the infotainment system.”

And, of course, what type of fuel the car requires.

If you’ve misfueled your car, there’s a way to reduce your costs. Ernesto Suarez, managing director of U.K. travel insurance company Halo Insurance Services, says you can call a local garage to tow your rental car to the nearest service center. In Europe, draining and cleaning the engine cost about $300 and can take an entire day.

“It’s always good practice to contact the rental car company to let them know what you are up to,” Suarez adds.

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Of course, misfueling isn’t the only common car rental mistake. They also include failing to take pictures of your car before and after your rental term, failing to plan for an extra driver and failing to understand the economics of rental cars.

“Always take pictures of all sides of the cars and inside the car to document any damage before pickup and after drop-off,” says Michael Stalf, managing director of Myonecar, a German car rental company.

Why take vacation photos of your car? Because your rental car company probably won’t. If it finds damage to your vehicle, it will hold you liable. By the way, if you find a ding, dent or scratch on your car when you pick it up, make sure it’s documented in your paperwork. Or better yet, ask for a different vehicle.

Some car rental companies have started to take pre- and post-rental images of their vehicles. Andy Abramson, a frequent business traveler who runs a communications firm in Los Angeles, rented several cars in Europe this spring. Some companies have new scanning equipment that captures an image of your vehicle before you leave and when you return.

Renters also tend to forget that car rental companies charge hefty fees for additional drivers. For example, Hertz charges $13.50 per day, a maximum of $189 per rental, for each additional driver. Julie Demaret, a director at the car rental firm Rhinocarhire, says you need to think about the extra driver before you rent.

And look out for upsells. For example, insurance can add $20 or more per day to the cost of your rental. But you can get car rental coverage for about half that from a traditional travel insurance company. Allianz Travel Insurance has a product called Rental Car Damage Protector for $11 a day. The insurance site iCarhireinsurance.com, which is operated by Halo Insurance, even sells a policy that covers you up to $1,200 for misfueling your car.

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Make sure you understand the tricks of the trade, too. Car rental companies get busy during the summer. Nicole Gustas, a frequent traveler from Boston, couldn’t find a rental car in Los Angeles recently, so she used a strategy that became popular last summer: She rented a U-Haul truck for two days. Then she found an SUV through Enterprise at a remote, off-airport location.

“We wanted an economy car,” says Gustas, a marketing director for an insurance company. “But beggars can’t be choosers.”

Following the basic rules of car rental etiquette is particularly important now, not only because car rental companies have gotten stricter about adding cleaning fees for vehicles left dirty, but also because the continuing car rental shortage has resulted in fleets that are older than they’ve been in years.

“Etiquette is all about being mindful of other people, which certainly includes being mindful of the person who is going to be renting the car after you,” says Nick Leighton, an etiquette expert and co-host of the weekly podcast “Were You Raised By Wolves?”

But perhaps the biggest mistake you can make when it comes to your rental car is underestimating your budget.

“Be prepared to spend money,” warns Robert Walden, editor-in-chief of VehicleFreak.com, a car-maintenance site.

Walden says higher prices aren’t the only thing to worry about. Vehicles will be in short supply, a sequel to last summer’s car rental shortage. That means some of us won’t even have the chance to make these common car rental mistakes.