Putting the wrong fuel into a rental car is surprisingly easy to do.
You may be tired after a flight, unfamiliar with the vehicle or simply pick up the wrong fuel nozzle at a Spanish petrol station.
Perhaps you have put petrol into a diesel car, or diesel into a petrol vehicle.
Whatever has happened, the most important advice is:
DO NOT START THE ENGINE.
If you realise the mistake while you are still at the petrol station, leave the vehicle switched off and contact Blanca Cars immediately.
The Blanca Cars FAQ specifically instructs customers who have put the wrong fuel into a rental car to stop using the vehicle immediately and contact the emergency service on +34 653 221 333 for assistance. Blanca Cars’ current FAQ also states that a €300 incorrect-fuelling fee applies.
Acting quickly can make a major difference.
The Most Important Rule: Don’t Start the Car
If you realise you have used the wrong fuel before starting the engine, you are in the best possible situation.
Do not:
- Start the engine
- Press the start button
- Switch the ignition on
- Try to drive away
- Add more of the correct fuel to dilute the mistake
Leave the car where it is and tell the petrol-station staff what has happened.
The Spanish motoring organisation RACE advises drivers who discover the mistake at the pump not to move or start the vehicle and to arrange roadside assistance instead. Driving with the wrong fuel can allow it to circulate through the fuel system and increase the risk of mechanical damage.
For Blanca Cars customers, your next step should be to contact us.
Step 1: Tell the Petrol Station Staff
If you are still beside the fuel pump, let a member of staff know that you have put the wrong fuel into the vehicle.
Do not feel embarrassed.
It happens to many drivers.
The petrol station may need to manage the pump area while assistance is arranged.
Do not attempt to push or move the vehicle unless the petrol-station staff and Blanca Cars or roadside assistance specifically tell you how to proceed.
Step 2: Contact Blanca Cars Immediately
Call the Blanca Cars emergency service:
+34 653 221 333
Explain clearly that you have put the wrong fuel into the rental vehicle.
Tell us:
- Your name
- Your vehicle
- Your location
- The petrol station name if known
- Whether the car is petrol or diesel
- Which fuel you accidentally used
- Approximately how many litres were added
- Whether the engine has been started
- Whether you have already driven the vehicle
The more information you provide, the easier it is to determine what assistance is required.
Blanca Cars’ current FAQ tells customers to stop using the car immediately and contact the emergency service after incorrect fuelling.
Step 3: Keep Your Fuel Receipt
Keep the receipt from the petrol station if you have it.
The receipt may show:
- Fuel type
- Number of litres
- Time
- Petrol station
- Amount paid
This can help establish exactly what fuel was added and approximately how much entered the tank.
If you do not have the receipt, make a note of the pump number and fuel type if you can do so safely.
What If You Have Already Started the Engine?
If you realise the mistake after starting the engine but before driving away:
Switch the engine off immediately.
Do not leave it running while you call for help.
Do not repeatedly restart it to see whether it sounds normal.
Contact Blanca Cars and explain that the engine has already been started.
The important thing now is to prevent the incorrect fuel from circulating any more than necessary.
What If You Have Already Driven Away?
Sometimes a driver does not realise the mistake until the car has already left the petrol station.
You may notice:
- Loss of engine power
- Rough running
- Unusual noises
- Smoke
- Difficulty accelerating
- Engine warning lights
- The engine stopping completely
If you suspect you have used the wrong fuel while driving:
Stop using the vehicle as soon as it is safe to do so.
Do not try to reach your accommodation simply because it is only a few kilometres away.
Driving further can potentially increase the damage.
RACE warns that using petrol in a diesel engine, for example, can affect components such as the fuel-injection system and pump if the vehicle continues to be driven.
Move the vehicle to the safest available location and switch off the engine.
Then contact Blanca Cars.
What If the Car Stops on a Road or Motorway?
If the vehicle becomes immobilised on a Spanish road after incorrect fuelling, roadside safety becomes your first priority.
Switch on your hazard warning lights.
Move away from active traffic if the vehicle can still be moved safely.
If the vehicle is immobilised on the road, use the connected V-16 emergency beacon supplied with the vehicle where required.
The beacon should preferably be placed on the roof of the vehicle, where its flashing light has maximum visibility.
Since 1 January 2026, the connected V-16 has been the legal warning device for immobilised vehicles covered by the Spanish requirement, replacing traditional warning triangles. It also transmits the vehicle’s location to the DGT 3.0 system.
Once you are safe, contact Blanca Cars.
For more detailed information, read:
Rental Car Breakdown on a Motorway in Spain: Step-by-Step Guide
Petrol in a Diesel Rental Car
Putting petrol into a diesel vehicle can cause problems because diesel fuel also plays an important lubricating role within parts of the fuel system.
If the engine is started and the incorrect fuel circulates, components in the diesel injection system can potentially be damaged.
RACE specifically warns that continuing to drive a diesel vehicle containing petrol can cause serious problems with systems including the fuel pump and injection system.
The safest response is therefore:
Do not start the engine.
Do not drive the vehicle.
Contact Blanca Cars.
Diesel in a Petrol Rental Car
Putting diesel into a petrol car is less common, partly because fuel nozzles and filler openings can differ in size, but mistakes are still possible.
If it happens, do not assume the car will be fine because the engine starts.
Do not attempt to drive until Blanca Cars or the authorised assistance provider has assessed the situation.
The correct solution may involve draining and cleaning the fuel system before the engine is operated again.
Don’t Try to Dilute the Wrong Fuel
A common idea is to fill the rest of the tank with the correct fuel and hope that this will dilute the mistake.
Do not do this.
You do not know whether the amount of incorrect fuel is small enough to be harmless, and continuing to operate the vehicle could turn a simple fuel-draining job into a much more expensive mechanical problem.
Contact Blanca Cars before taking any further action.
Don’t Try to Drain the Fuel Yourself
Do not attempt to siphon fuel from a rental car.
Petrol and diesel are flammable substances and must be handled correctly.
You could also damage the fuel system or create a spill at the petrol station.
Fuel removal should be handled by an authorised professional.
Do not call an independent mechanic or fuel-drain company without first speaking to Blanca Cars.
How Can You Avoid Putting the Wrong Fuel in a Rental Car?
The best way to deal with incorrect fuelling is to prevent it happening in the first place.
Before visiting a petrol station, make sure you know which fuel the vehicle uses.
Look for information:
- On the inside of the fuel filler flap
- Around the filler cap
- In the vehicle information supplied with your rental
- On labels inside the car
If you are unsure, contact Blanca Cars before filling the tank.
Do not guess.
Understanding Fuel Labels in Spain
Spanish petrol stations use familiar names such as gasolina for petrol and gasóleo or diésel for diesel.
You may also see European fuel labels.
Petrol can be labelled E5 or E10, while diesel is commonly identified by labels such as B7. Spain’s Ministry for Ecological Transition lists petrol grades including E5 and E10 and identifies Gasóleo A as a common road diesel fuel.
If you have any doubt about which pump to use:
Stop and check before you start filling.
Thirty seconds spent confirming the fuel type can prevent a much larger problem.
Is Wrong Fuel Covered by the Rental Price?
Incorrect fuelling is considered a customer-related incident rather than an ordinary technical failure.
The Blanca Cars FAQ currently states that a €300 fee applies when the wrong fuel is put into the rental vehicle.
Additional damage or costs may depend on what has happened, particularly if the vehicle was driven after being incorrectly fuelled.
For that reason, stopping immediately is important both mechanically and financially.
Always refer to the current Blanca Cars rental terms and contact us for guidance about your particular situation.
Frequently Asked Questions
What Should I Do If I Put the Wrong Fuel in a Blanca Cars Rental Car?
Stop using the car immediately and contact Blanca Cars on +34 653 221 333.
I Haven’t Started the Engine. Is That Better?
Yes.
If you notice the mistake before starting the vehicle, leave the engine and ignition switched off and contact Blanca Cars.
Can I Add the Correct Fuel to Dilute the Wrong Fuel?
No.
Do not add more fuel or attempt to correct the problem yourself.
Can I Drive to My Hotel or Villa?
No.
If you know or suspect that the wrong fuel is in the vehicle, stop using it and contact Blanca Cars.
What If I Only Added a Small Amount?
Still contact Blanca Cars.
Do not decide for yourself that the quantity is too small to cause a problem.
Can I Arrange My Own Fuel Drain?
Not without first speaking to Blanca Cars.
Contact us so the correct assistance can be arranged.
Is There a Charge for Putting the Wrong Fuel in a Blanca Cars Vehicle?
The Blanca Cars FAQ currently states that a €300 incorrect-fuelling fee applies.
Remember: Wrong Fuel Means Stop
If you put the wrong fuel into your rental car in Spain, remember these simple steps:
DO NOT START THE ENGINE.
DO NOT DRIVE THE VEHICLE.
DO NOT TRY TO DILUTE THE FUEL.
DO NOT ATTEMPT TO DRAIN IT YOURSELF.
CONTACT BLANCA CARS IMMEDIATELY.
If you have already started or driven the vehicle:
STOP AS SOON AS IT IS SAFE TO DO SO AND SWITCH THE ENGINE OFF.
The earlier the mistake is identified, the better.
Putting the wrong fuel into a rental car is frustrating, but making the right decision immediately afterwards can help prevent the problem becoming considerably worse.
If you are driving a Blanca Cars vehicle and have accidentally used the wrong fuel, contact our emergency service on +34 653 221 333 and follow the instructions provided.