Rental car fuel policy explained: full-to-full vs. full-to-empty

You’ve reserved the rental car, compared the price and sorted out your deposit. And then, when you pick up the car, one more choice comes your way that’s easy to overlook: the fuel policy. Which fuel option do you pick? Do you refuel yourself before returning the car, or do you pay for the tank upfront? That single decision at the counter can make a difference of a few dozen euros, and sometimes more than that. Many people sign for it routinely, without grasping the consequences.

In this guide we explain thoroughly how a fuel policy works, what the difference is between full-to-full and full-to-empty (prepaid), which in-between variants you might come across and why full-to-full works out cheapest for most travellers. We look at a concrete worked example based on ratios, the charging policy for electric rental cars, regional differences in how the contract is worded and how to protect yourself with the right proof. At the bottom you’ll find a practical checklist.

What exactly is a fuel policy?

A fuel policy, also called a fuel agreement or fuel arrangement, is the agreement between you and the rental company about the amount of fuel in the tank when you pick up and when you return the car. It governs two things: the state in which you receive the car, and the state in which you have to return it. Sounds simple, but this is exactly where one of the best-known hidden costs of a car rental lurks.

The rental company wants certainty that the tank won’t be left empty for the next customer, and you don’t want to pay for fuel you never used. Those two interests sometimes clash. That’s why several arrangements exist, each with a different cost structure and a different amount of hassle. It pays to know which one you’ve agreed to before you leave, because at the counter it’s often presented quickly and in jargon.

Full-to-full: refuel yourself before returning

With full-to-full (often written full to full) you receive the car with a full tank and return it full as well. You only pay for the fuel you put in yourself along the way, at the normal price at an ordinary petrol station. This is by far the most transparent and usually the cheapest arrangement.

The principle is fair: you pay for what you use, no more. The only condition is that you stop at a petrol station just before returning the car to fill the tank right back up. If you don’t return it completely full, the rental company tops it up, but at their own rate plus often a service charge (more on that later). Full-to-full therefore takes a little planning, but rewards you with the lowest total cost.

Full-to-empty (prepaid): pay for the tank upfront

With full-to-empty, also called prepaid or full to empty, you pay for a full tank straight away at pick-up. You receive the car full and may return it as empty as you like. In theory that sounds convenient: no detour to the petrol station, no stress just before your flight.

In practice there are two catches. First, you pay for the fuel at the rental company’s rate, which is usually higher than the pump price, and sometimes a separate service charge is added on top. Second, and this is the biggest drawback, you rarely get anything back for the fuel you don’t use up. If you return the car with a quarter of a tank, you’ve paid for that fuel but not used it. Unless the contract explicitly promises a refund (rare), everything left in the tank is a gift to the rental company.

The in-between variants you might come across

Besides the two main forms, several in-between arrangements circulate. It’s worth recognising them, because the wording varies greatly from one rental company to another and from one country to another.

• Full-to-same-level. You receive the car with, say, half a tank and have to return it at exactly that level. This involves estimating and guessing, because bringing the needle back to exactly the right spot is tricky.
• Half-full or quarter-tank arrangement. Some local rental companies don’t hand over the car completely full. In that case read carefully which level you need to return it at.
• Prepaid with refund. The odd rental company promises a refund for unused fuel, often at a lower rate and sometimes with a fixed deduction. Don’t count on this blindly without seeing it in writing.

The common thread: the vaguer the agreement, the more room there is for dispute or extra costs. Full-to-full remains the clearest.

Why full-to-full is usually the cheapest

Full-to-full wins on two fronts. First, you pay the actual pump price instead of the rental company’s fuel rate, which is usually higher. Second, you avoid paying for fuel you don’t use, which is almost unavoidable with prepaid, because you never return the tank perfectly empty (and you can’t safely plan to either).

Prepaid is in principle only worthwhile in one very specific scenario: if you’re certain you’ll run the tank almost completely empty and the rental company’s fuel rate happens to be no higher than the pump. In practice that’s a rare combination. For the vast majority of trips, certainly short or medium ones, prepaid makes you pay for air. If you want to dig deeper into pitfalls like these, also read our 12 tips to avoid hidden costs.

A worked example based on ratios

Because fuel prices and rental rates fluctuate constantly, we work here with ratios instead of made-up exact amounts. The mechanism is what matters.

Suppose you rent a car with a tank of around 50 litres. With prepaid you pay for all 50 litres straight away. Suppose the rental company’s fuel rate is roughly 15 to 20 percent above the normal pump price (a common order of magnitude, not a fixed rule). Then you’re already paying 15 to 20 percent too much for that full tank before you’ve driven a single kilometre.

Now suppose that during your trip you only use up two thirds of the tank and return the car with a third of fuel left. With prepaid and no refund, you lose that remaining third entirely. Do the maths: you pay the higher rate over the full tank, and on top of that you lose the value of a full third. With full-to-full, by contrast, you’d only have filled up those two thirds, at the normal pump price. The difference between the two scenarios quickly adds up to a significant chunk of your total fuel budget. The less you drive, the bigger that prepaid disadvantage becomes.

Refuelling and service charges for not returning the car full

If you choose full-to-full but still don’t return the car completely full, the rental company tops up the missing litres. They rarely do that for free. Usually expect two components: the price per missing litre at their own, higher rate, plus a fixed refuelling or service charge (a refuelling charge or service fee). That fixed charge can climb steeply and is unrelated to how many litres were missing. Even a few missing litres can land you with a disproportionately high bill.

That makes it all the more important, with full-to-full, to genuinely fill the tank completely just before returning the car. A tank that’s only just short of full often already counts as not full for the rental company, with the full service charge as a result. The effort of those last few litres is therefore small compared with what you risk paying.

How do you provide proof with full-to-full?

Disputes about the fuel level are among the most common arguments after a car rental. You can easily protect yourself with two types of proof.

• The fuel receipt. Fill up close to the drop-off point, ideally within a few kilometres, and keep the receipt. It shows the time, location and number of litres. This proves the tank was full shortly before return. A receipt from 80 kilometres away is less convincing.
• A photo of the gauge. Just before you leave the car, take a clear photo of the dashboard showing the full fuel gauge (and preferably the odometer). A short video panning around the car can also help.

Keep this proof until your credit card statement comes in and any deposit has been fully released. If an unjustified fuel charge does appear, you’ll have something to show. This ties in with how you protect your deposit, which we cover further in our guide on excess and deposit.

The charging policy for electric rental cars

For electric rental cars there’s a variant on the fuel policy: the charging policy. The logic is similar, but the details differ. Some rental companies use a comparable full-to-full principle (you return the car with the same charge percentage as at pick-up), others work with a fixed charging rate or a prepaid-style formula where you pay for a full battery upfront.

With electric, pay extra attention to a few points. Charging takes longer than refuelling, so allow enough time before you reach the drop-off point. The terms for returning the car are often expressed in charge percentages rather than litres. And the cost of topping up by the rental company can, just as with fuel, be higher than public charging rates, sometimes with a separate service charge. Ask about the charging policy explicitly, because it’s less standardised than the classic fuel policy.

Regional differences and the wording in the contract

The terms used vary by country and by rental company. In English you’ll come across full to full, full to empty, prepaid fuel, same to same and fuel purchase option. In Southern European destinations prepaid is more often actively offered or even presented as the standard, while elsewhere you’ll more often see full-to-full as the norm. The sales pitch at the counter can be strong: prepaid is sometimes presented as the easy or cheaper option, while for you it usually isn’t.

So always read the exact wording in your voucher and in the rental contract before you sign. Check three things: the state in which you receive the tank, the state in which you have to return it, and whether there’s a refund for unused fuel. If you’re unsure about a term at the counter, ask them to explain in plain language what happens if you return the car full versus empty. Don’t let yourself be talked into a more expensive arrangement under time pressure.

Full-to-full versus full-to-empty at a glance

Frequently asked questions

Is full-to-full always cheaper than prepaid?

In most cases yes, because with full-to-full you pay the normal pump price and only for your own usage. Prepaid can only break even in an exceptional scenario: if you run the tank almost completely empty and the rental company’s rate is no higher than the pump. That combination is rare, so as a rule of thumb full-to-full is the safest choice.

What happens if I don’t return the car completely full with full-to-full?

The rental company then tops up the missing fuel, usually at their own higher rate, and often with a fixed refuelling or service charge on top. That fixed charge is unrelated to the number of missing litres, which means even a small shortfall can work out relatively expensive. So fill the tank up completely just before you return the car.

Do I get money back for unused fuel with prepaid?

Usually not. With the classic prepaid arrangement, whatever’s left in the tank goes to the rental company. Some rental companies offer a variant with a refund, but don’t count on it unless it’s explicitly stated in writing in your contract, because there’s often still a rate or fixed deduction taken off.

How do I prove I returned the car full?

With two things: a fuel receipt from a station close to the drop-off point (with time, location and number of litres) and a photo of the full fuel gauge on the dashboard, preferably with the odometer in shot. Keep this proof until your deposit has been fully released, so you have something to fall back on in a dispute.

Does the fuel policy also apply to electric rental cars?

With electric cars people refer to a charging policy instead, but the logic is similar. Sometimes it’s comparable to full-to-full (return the car with the same charge percentage), sometimes prepaid-style. The terms are expressed in charge percentages and topping up by the rental company can be more expensive than public charging. Ask about the policy explicitly and allow enough charging time.