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Should You Decline Prepaid Fuel When You Rent a Car? The Answer, Once and for All | Frommer's Shutterstock / dondesigns

Should You Decline Prepaid Fuel When You Rent a Car? The Answer, Once and for All

When a rental car agent pressures you into prepurchasing gas, should you do it?

It's a dreaded moment that comes every time you approach a car rental counter: the part where the agent pressures you to accept the prepaid fuel deal.

The pitch seems convincing. If you accept the offer, you won't have to fill up before returning the vehicle! Pay for a full tank now and you'll be done! Our prices are competitive with local gas stations! We take care of everything! Just sign here.

For people who hate confrontation, saying no to the so-called "fuel service option" can be a challenge. 

But if you want to save money, you should always say no.

To make you feel better about dashing that agent's hopes, here's why.

You'll almost never return the car with a completely empty tank. 

The premise of prepaid fuel offers is that you pay the company's price for what's in the tank at the time of rental. But you're pretty much guaranteed not to use precisely that amount of fuel on your travels.

So if you take the deal, you'll inevitably return the car with a tank containing extra gas you paid for with the package. That's nothing more than funneling money to the rental company. 

Many rental agencies quote prices wrong.

As discount rental agent AutoSlash notes, the "pump price" might be a lie or, at the least, based on the worst-case price near the airport, where gas stations frequently gouge customers.

You'll probably find a better per-gallon price on your own.

Rental companies like claiming their rates are "comparable" (Avis) or "competitive" (Hertz) with local rates, but those adjectives don't really mean anything. The word almost never used is "lower."

Even rental companies that do quote accurate or truly comparable prices know full well they'll still make money off this option because, again, almost no renters return their cars with completely empty tanks, so customers are essentially giving the rental giants fuel.

You can't get your money back for fuel you didn't use.

Even though you are nearly certain not to use all the fuel you buy on a fuel service option, none of the major renters will pay back the difference. 

Hertz and Dollar are so adamant about it they scream the warning in all caps on their official websites: "NO REFUND WILL BE GIVEN FOR UNUSED FUEL."

We get it, Hertz and Dollar! Once the cash is grabbed, you won't let go.

The car's tank capacity might be recorded incorrectly.

Incorrect tank capacity calculations might date to the day the car arrived on the rental lot. As AutoSlash explains, "When the delivery truck rolls in with a load of new cars, the fleet manager loads all the information about that car into the computer—often quickly, and sometimes making assumptions about the car’s specifications. If they are lazy or make a mistake, you can be overcharged for extra gallons."

Alamo admits to such radical imprecision right off the bat. The company's official info says customers are charged an "estimate" based on "average tank size for the car class." In other words, the estimate is not tailored to your specific vehicle.

You might pay for a "full" tank that isn't actually full.

In newly refueled cars, "full" almost never means full. Everyone who drives a car knows that after a tank is filled up, there may be a long period of time during which you drive the car for miles and miles but the gas gauge won't start dipping below full.

Guess what? People who rent cars know about this buffer period, too, and many people return their cars after driving them for 10 or 20 miles following the final fill-up. You've probably done this yourself. It's why some rental companies now want to see a receipt for your gas.

If a fuel gauge indicates a full tank, rental agencies rarely top it off before renting the car again. Why would they bother? It looks full. Yet if you prepay for the fuel service option, which ostensibly covers a completely full tank, you'll be paying for gas that was never there during your rental.

Over multiple cars, that adds up to a lot of free gas that customers hand over to the renter. It's another hidden way that agencies are guaranteed to make major bank off prepaid fuel options.

You could always try forcing staff members to top off the tank of a new rental to ensure you start with a certifiably full load of gas, but who are we kidding? You're too busy and so are they.

Taxes on fuel might be higher at the rental desk.

If you've ever rented a car at an airport, you've probably noticed how high the taxes and fees can be there. That's usually by law, affecting anything you buy at the rental car desk, including options like gas.

But if you buy your fuel independently away from the airport orbit, that special, higher tax rate won't be imposed on your gas.

Beware the EZFuel scam.

Because so many customers who are capable of performing basic arithmetic decline the prepaid fuel option, some of the big rental companies have devised a new trap: the forced refuel option.

Avis and Budget calls theirs EZFuel, but it's not easy and it's not optional. It works like this: If you drive less than 75 miles during your rental, the company will charge you $16 to $20 unless you return with a full tank and present a receipt for your refueling. Because this rule is hidden in the fine print that you (probably hastily) scrolled through and initialed when you rented the car, you have to abide by the rule whether you want to or not.

For Avis and Budget, EZFuel is a default. You are required to accept it, and the only way to get out of it is to be armed with that receipt when you return the vehicle. 

We hear complaints from travelers who return vehicles with a full tank of gas but still get hit with the surcharge. Getting a refund requires the hassle of contacting the company via phone calls and emails.

To protect yourself from forced surcharges like EZFuel, Frommer's recommends that you take photos of four things when you return the car: the full fuel gauge, the odometer, your fuel receipt, and the car itself. With that evidence you can prove that you did what's required to avoid the charge and that you're not responsible for any erroneous damage claims.

Having that paperwork may not ensure you avoid unethical surcharges after your rental, but you will have the ammunition you need to dispute the charges successfully. 

When prepaying for gas makes sense

There is only one situation in which you should prepurchase fuel from your renter, and that is when you don't care about saving money. 

Sure, prepaying buys you the convenience of returning your car with an empty tank, so if you're severely pressed for time prepaying can hurry things along (for a fee). But there's almost never a scenario in which you wouldn't be able to find cheaper gas within range of the rental lot.

Simply keep your eyes peeled for cheaper gas stations during the rental period. Or use a free app or website to find stations that charge much less than what the rental car company wants you to fork over. You can consult GasBuddy, Waze (click the fuel pump icon for local prices), Upside, or Google Maps (search for gas or petrol, depending where you are).

And keep your receipt, particularly for Avis and Budget.

One thing you must never do is return a rental car with an empty tank if you haven't purchased a fuel plan. If you do that, you'll not only have to pay the inflated gas price but also a service fee for the staff to fill 'er up.

The next time you're tempted to sign on the dotted line for a prepaid fuel service option, ask yourself: Just how lazy am I?