If you put the wrong fuel in a rental car, do not start the engine, or switch it off as soon as it is safe.
- Call the rental company's roadside assistance number before anyone drains the tank, so the costs are agreed.
- Misfuelling is often excluded from the rental company's damage cover, so the draining and any repair can fall on you.
- Keep the fuel receipt, photos and every invoice in case you need to check the bill later.
It takes one second at an unfamiliar pump: a green nozzle that is diesel in one country, a hire car you have only driven for an hour, and a tank full of the wrong fuel. If you notice it in time, do not start the engine: that one step can save you most of the cost. Here is what to do next, why the bill often lands with you, and how to check it afterwards.
Why misfuelling is so expensive
Diesel and petrol engines work differently. The AA explains that it is worse to put petrol in a diesel car than diesel in a petrol car, and that in both cases the damage grows the longer the engine runs. Diesel in a petrol car can damage the catalytic converter. Petrol in a diesel can make the engine run erratically or stall.
If you have not started the engine, the fix is usually draining and flushing the tank. Once fuel has circulated through the system, parts may need cleaning or replacing, and the car can be off the road for a while.
Is wrong fuel covered by rental insurance?
Often not. When Which? checked excess waivers sold by car hire firms in 2024, it found several policies that did not cover misfuelling, alongside exclusions for the underbody and lost keys. If your contract lists misfuelling as an exclusion, the excess waiver does not apply to it at all, whatever the excess level.
| Who might pay | When |
|---|---|
| You, in full | Misfuelling is excluded from the rental company's cover |
| Your excess insurance | If your own standalone policy lists misfuelling as covered |
| Your credit card cover | Only if its terms include it |
ECC-Net points out that the contract should detail what is and is not covered. Check your own terms before you rely on any cover. Our terms check helps you find the clause.
What to do if you put in the wrong fuel
Do not start the engine
If you realise at the pump, leave the key out of the ignition. If you are already driving and the car starts to judder or a warning light comes on, the AA advises switching off as soon as it is safe.
Move the car only by pushing it
Put the car in neutral and, with help, push it to a safe spot away from the pumps. Tell the station staff what happened.
Call the rental company's assistance number
The number is usually on the key fob, the windscreen sticker or the contract. Explain what happened, which fuel went in, and roughly how much. Ask who will drain the tank, what it costs, and whether you can continue in the same car afterwards. Note the name of the person you speak to and the time of the call.
Collect your evidence
Take photos of the pump, the nozzle label and the fuel cap. Keep the fuel receipt. Ask for a written invoice from whoever drains the tank. If the company replaces the car, photograph the new car at pick-up as well.
Check the bill before you pay it
A misfuelling bill can combine several items: draining, recovery, a replacement car, repairs and loss of use. Ask for an itemised invoice and proof that each repair was carried out. If an amount looks high, our amount check helps you compare it, and our guide on repair invoices versus estimates explains what to ask for.
How to avoid it in the first place
- Check at pick-up. ECC Malta suggests checking which fuel the car takes, as this is often shown on the fuel tank door. Ask the desk if you are unsure, and note it on your phone.
- Learn the EU fuel labels. Since 12 October 2018, fuel labels have been standardised across Europe: petrol in a circle (E5, E10), diesel in a square (B7, B10, XTL) and gaseous fuels in a diamond. The label is on the pump nozzle and, on newer cars, next to the fuel cap.
- Do not trust colours. Nozzle colours differ between countries and brands. Read the label, not the colour.
- Refuel calmly. Most mistakes happen when tired, rushed, or on the way to the return. Read our guide to fuel policies so you know when and where to fill up.
If you only notice after the return
Sometimes the company finds wrong fuel in the tank after you drop the car off. Ask for evidence: a fuel sample, a workshop report and the date the problem was found. Compare it with your last fuel receipt. If your receipt shows the correct fuel, use it in a written objection. Our guide on disputing a damage claim walks you through it.
A short example
You fill a rental diesel with about 10 litres of petrol in Portugal and notice before starting. You push the car aside, call the assistance number, and the company sends a recovery truck. Later it charges you for draining the tank and the call-out, with an itemised invoice. Your excess waiver does not cover misfuelling, but your standalone excess policy does, so you send the invoice and your fuel receipt to your insurer. Our guide to claiming the excess back shows what to include.
Frequently asked questions
Is petrol in a diesel worse than diesel in a petrol car?
Generally yes. The AA says it is worse to put petrol in a diesel car than diesel in a petrol car. In both cases, the damage grows the longer the engine runs, so not starting the engine is the most important step.
Does zero excess cover at the desk include wrong fuel?
Not always. In its 2024 check of desk excess waivers, Which? found several policies that did not cover misfuelling. Read the list of exclusions in your own cover before you rely on it.
Can I call my own breakdown service for a rental car?
It is safer to call the rental company first. Your contract usually lists its own assistance number and may say that repairs need its consent. Agreeing the next step with the company avoids a dispute about who arranged what.