What Happens When You Put the Wrong Fuel in Your Car

Wrong Fuel in Your Car and How to React

Putting the wrong fuel into a vehicle, known as misfuelling, is a common issue for many drivers across the UK. This error can result in severe damage to an engine, leading to expensive repair bills. Understanding how to limit this damage, spotting the warning signs of incorrect fuel usage, and knowing the right steps to take can help save significant trouble and money.

The Immediate Steps After Misfuelling Your Vehicle

If you suspect you have put the wrong fuel in your vehicle, acting quickly makes a significant difference. Here are the key actions to consider right away:

Do Not Start the Engine

Starting the engine allows the incorrect fuel to circulate throughout the system, potentially causing further damage. Leave the ignition off. If you have already started the engine and realised the mistake, turn it off as soon as possible.

Recognise the Signs of Incorrect Fuel

After starting the engine, your vehicle might show specific indicators that something is wrong. Watch for unusual noises, a noticeable decrease in acceleration, or dashboard warning lights illuminating. These signals suggest you might have filled up with the wrong type of fuel.

Seek Professional Assistance

When you discover misfuelling, contact a professional service without delay. Specialists can drain the fuel system, reducing the likelihood of lasting engine damage. Services like RAC Fuel Assist are equipped to handle these situations, often aiming to get drivers back on the road as promptly as possible.

How Common is Misfuelling in the UK?

This type of mistake happens more often than many people realise. According to figures from motoring organisations, around 150,000 drivers in the UK misfuel their vehicles each year, with incidents occurring roughly every three and a half minutes.

Most of these incidents—over 95%—happen when petrol is put into a diesel vehicle. This is because a petrol pump nozzle fits easily into the filler neck of a modern diesel car. Conversely, diesel pump nozzles are generally wider. They will often not fit into a petrol car’s filler neck, making it less likely for diesel to be put into a petrol vehicle by mistake, as highlighted by The AA.

Does Car Insurance Cover Misfuelling?

Many breakdown companies possess the necessary equipment to address misfuelling situations. While you wait for assistance, it’s helpful to contact your insurance provider to verify your policy details. Some comprehensive car insurance plans do include cover for misfuelling, though this is not always a standard feature. Reviewing your policy wording clarifies whether this type of incident is covered, as suggested by Compare the Market.

What are the Consequences of Using Incorrect Fuel

The extent of damage from misfuelling varies depending on several factors, including the amount of incorrect fuel added, the distance the vehicle was driven, and whether the engine seized or was shut off quickly.

If the vehicle has not been started, the process typically involves draining the incorrect fuel and refilling it with the correct type. This usually resolves the issue.

 

Driving with the wrong fuel, however, can lead to more significant damage. Petrol, when mixed with diesel, acts as a solvent, reducing the lubrication properties of the diesel. This can cause components, such as the fuel pump, to overheat and wear out. For petrol vehicles, diesel can clog fuel filters and injectors. In cases of severe damage, the car might require towing to a mechanic for a thorough inspection and more extensive repairs.

How Can Drivers Prevent Misfuelling?

Preventing misfuelling involves simple but consistent habits:

• Double-Check the Pump: Before inserting the nozzle, take a moment to confirm you are selecting the correct fuel type.
• Refer to Your Car’s Manual or Fuel Cap: Many vehicles have the fuel type clearly marked on the inside of the fuel flap or on the cap itself.
• Maintain Awareness: Avoid distractions at the petrol station. A quick second of inattention can lead to a costly error.
• Consider Anti-Misfuelling Devices: Devices are available that fit into the fuel filler neck, designed to prevent incorrect nozzle sizes from entering your tank. For example, some devices are specifically designed to prevent petrol from being put into a diesel car.

Beyond physical devices, simple habits at the petrol station offer additional layers of protection against misfuelling.

How Can I Avoid Putting the Wrong Fuel in My Vehicle?

Maintaining a few straightforward checks can significantly reduce the risk of misfuelling.

• Verify the Fuel Pump Handle: Before you begin, always check the pump handle itself. Most stations clearly display the fuel type directly on the handle.
• Confirm Pump Labels: Every fuel pump has clear labels indicating the type of fuel it dispenses. Take a moment to read this information thoroughly. This includes details like “Petrol” or “Diesel,” alongside specific grades like “Unleaded 95” or “Diesel B7.”
• Keep Your Receipt: After refuelling, check your receipt. It confirms the type of fuel dispensed, offering a final verification step.

Staying alert and following these checks can help prevent a common and often expensive mistake, as outlined by motoring organisations like The AA.

Frequently Asked Questions About Misfuelling

What Happens if You Put the Wrong Fuel in a Car?

Putting the wrong fuel in a vehicle can cause severe damage, depending on the fuel types involved and how long the engine runs. If petrol is put into a diesel car, the diesel fuel pump and injectors can be damaged as petrol lacks the lubricating properties of diesel. Conversely, putting diesel into a petrol car often means the heavier diesel fuel won’t ignite properly, potentially clogging the fuel system and damaging the catalytic converter. Aviva – a leading vehicle insurance provider – advises detailing these consequences.

What Should I Do Immediately After Misfuelling?

If you realise you have put the wrong fuel in your car, do not start the engine. Starting the engine circulates the incorrect fuel through the system, increasing potential damage. Keep the engine off, put the car in neutral, and push it to a safe spot. You should then contact your breakdown provider or a specialist fuel drainage service. Many services operate nationwide to help with wrong fuel recovery.

Can Misfuelling Permanently Damage My Engine?

While misfuelling can cause significant damage, it does not necessarily lead to permanent engine damage if handled quickly and correctly. The severity depends on the type of fuel, the amount of incorrect fuel, and whether the engine was started or driven. Prompt fuel drainage and system flushing by professionals often prevents lasting issues. However, ignoring the problem or continuing to drive can result in extensive repairs, including replacing fuel pumps, injectors, and filters, as noted by Confused.com’s guide on wrong fuel.

How Can I Easily Distinguish Between Petrol and Diesel Pumps?

Beyond checking the labels, most petrol pumps have a thinner nozzle designed for smaller petrol tank openings, whereas diesel nozzles are typically thicker. This physical difference helps prevent misfuelling, especially in newer vehicles with anti-misfuelling devices. Additionally, petrol usually has a green handle and diesel a black handle, although this colour coding can vary between petrol stations. Always refer to the fuel type written on the pump and your vehicle’s fuel cap as the most reliable identifiers.

Are There Any Common Misconceptions About Misfuelling?

A common misconception is that a small amount of incorrect fuel won’t cause harm. Even a small quantity can be problematic, especially for modern, highly sensitive engines. Another belief is that simply topping up with the correct fuel will fix the issue; this is rarely effective, as the incorrect fuel will still circulate. Always seek professional advice, either from a mechanic, your insurer, or an auto specialist, for a fuel drainage service to ensure all incorrect fuel is removed safely.