Petrol in a Diesel Car: The Consequences of Misfueling and What to Do:

Worried about having accidentally added a small amount of petrol to your diesel vehicle? If this is causing you concern, rest assured—you’ve come to the right place. This comprehensive article offers essential information and guidance to help you navigate the situation. In need of immediate assistance? Visit our Petrol in Diesel Car service page for 24/7 nationwide wrong fuel rescue service across the UK.

This article addresses the issue of mistakenly refuelling a diesel engine with petrol.

Ready for the solution? Keep scrolling to unveil the details.

Noticed Your Error at the Petrol Station?

The Misfueling Dilemma: What to Do When You Put Petrol in a Diesel Car

Accidentally filling a diesel vehicle with petrol is a common concern among motorists. If you’ve just realised this mistake after refuelling at a petrol station, it is vital to act promptly. Begin by switching off the engine, avoid starting or driving the vehicle, and ensure the car is securely locked. Operating the engine with the incorrect fuel can result in serious damage to critical internal components.

The fuel system is particularly vulnerable when petrol is introduced into a diesel tank. This situation is, unfortunately, a frequent occurrence for many drivers. Even if the ignition was briefly turned, there is a risk that components have been contaminated and the fuel pump may have initiated priming. Remain calm—there is a solution, and in most cases, the engine can be successfully recovered.

Realised Your Mistake After Leaving the Petrol Station?

If you become aware of the error after driving away from the forecourt, it is essential to park your vehicle safely and as promptly as possible. Avoid continuing your journey, as this could result in severe engine damage. While some older diesel engines may tolerate a small amount of petrol, it is not worth the risk. If you’re still near the station, consider asking staff for assistance in moving your vehicle to a secure location.

Once safely parked, switch on your hazard lights to alert other road users. There’s no need to panic—your vehicle is likely still in a recoverable condition. If it’s dark, also activate your sidelights to ensure visibility. Next, contact a breakdown or fuel drainage service for assistance. When speaking on the phone, be sure to face oncoming traffic to remain aware of your surroundings and ensure your safety.

Unsure Whether You’ve Added a Small Amount of Petrol to Your Diesel Vehicle?

If you’re uncertain whether you’ve mistakenly added petrol to your diesel tank, start by checking your fuel receipt—it should clearly indicate the type of fuel dispensed. There are also several signs that may help confirm the issue:

• The vehicle comes to an unexpected halt, despite appearing to be in good condition.
• You experience a sudden loss of power and are unable to start the engine.
• Once started, the engine may be difficult to turn off.
• Unusual or loud engine noises become apparent, particularly under load.
• The vehicle struggles to start or drive smoothly, especially when the engine is warm.

You can contact a professional to get a quote regarding this.

How to Prevent Putting the Wrong Fuel to Your Engine?

Accidentally adding petrol to a diesel engine is a common mistake made by many drivers—whether driving a two-wheel or four-wheel drive—particularly those who may be distracted or forgetful. If you’re seeking ways to avoid this issue in the future, a few simple preventative measures can help.

If purchasing a newer vehicle with built-in safeguards (such as some Ford models) isn’t within your budget, consider applying a clear indicator or label near the fuel cap. This serves as a helpful reminder of the correct fuel type—especially useful if multiple people drive the vehicle.

Diesel in a Petrol Engine

It is generally difficult to mistakenly fill a petrol vehicle with diesel due to the wider size of diesel pump nozzles, which typically do not fit into the narrower petrol filler neck. However, in the rare event that diesel is introduced into a petrol engine, it can lead to significant damage—particularly to the catalytic converter, which may require costly replacement.

To minimise potential harm, it is advisable to use a manual hand pump to drain the incorrect fuel as soon as possible. Prompt action can help prevent further contamination and protect the integrity of the engine.

How Does This Mistake Even Happen?

Many drivers find it difficult to distinguish modern diesel engines from traditional ones. If you are driving a vehicle that isn’t your own, or if you’re used to petrol cars, the differences can be subtle. Modern diesel engines tend to run more quietly and smoothly, closely resembling their petrol counterparts—unlike older diesel engines, which were often noisy, slow to warm up, and emitted more visible exhaust. As a result, drivers may forget they are operating a diesel vehicle due to the lack of distinct visual or audible cues.

Can I Dilute Petrol with Diesel?

Modern diesel vehicles are equipped with advanced high-pressure fuel injection systems, which are far more sensitive than older models. For this reason, diluting petrol-contaminated diesel with additional diesel fuel is not a safe or effective solution. Attempting to do so may cause significant damage to your engine and fuel system. If you decide to take matters into your own hands, it is essential to drain as much of the contaminated fuel as possible before considering any further action.

What If I’m Leasing My Vehicle?

If you are leasing your car, you are still fully responsible for any damage caused by misfuelling. Starting the engine after filling up with the wrong fuel is one of the most damaging mistakes you can make, particularly in a diesel vehicle. This can result in substantial repair costs, as damage to the fuel system and engine may require extensive and expensive work—often running into thousands of pounds.

Am I Covered by My Insurance?

Unfortunately, misfuelling is typically not covered under standard car insurance policies—even those offering comprehensive protection. It is always advisable to check the fine print or speak directly with your insurer to clarify whether misfuelling is included in your specific policy.

Am I Covered by My Breakdown Cover?

Vehicle manufacturers are generally not liable for accidental misfuelling, even in small amounts. However, many breakdown services may assist with towing your vehicle to a safe location or a nearby garage. Coverage can vary, so it is worth checking the details of your breakdown policy.

How Much Could This Mistake Cost?

Unfortunately, putting the wrong fuel into your vehicle can be an expensive error, with costs ranging from a few hundred to several thousand pounds. The total expense depends on various factors, including your location, whether the engine was started, and the extent of contamination. If you’ve filled the tank completely with the incorrect fuel, prepare for a potentially high repair bill.

How Much Does It Cost to Drain a Fuel Tank?

Wondering about the cost of removing petrol from a diesel vehicle? The price will vary depending on several factors, including your location, the extent of the contamination, and the provider performing the fuel drain service. It is recommended to request a quote from a reputable fuel recovery specialist to understand your options and associated costs.

What Happens If I Put a Small Amount of Petrol in a Diesel Engine?

Each year, over 150,000 vehicles in the UK are mistakenly filled with the wrong type of fuel—a costly error that leads to repair bills totalling millions of pounds. But what exactly happens when petrol is introduced into a diesel fuel system?

Petrol acts as a solvent within a diesel engine, stripping away the essential lubrication that diesel fuel provides. This lack of lubrication can cause increased friction and wear, particularly within the fuel pump and injectors. Additionally, petrol can damage the rubber seals and other sensitive components designed specifically for diesel use, potentially resulting in leaks and long-term damage.

Even a small amount of petrol can compromise the integrity of your diesel engine, so prompt action is essential to prevent costly repairs.

What To Do If I Put Wrong Fuel in my Diesel Engine?

Misfuelling is a common mistake made by many motorists, despite the efforts of petrol stations to colour-code fuel pumps clearly. If you suspect you’ve added petrol to your diesel vehicle, it’s crucial not to start the engine and to follow proper guidance before attempting any corrective action. For more detailed support, visit our Petrol in Diesel Car information page.

How to Drain Wrong Filled Fuel from a Car

You may ask for the assistance of a staff in the petrol area where you do misfuel. In this case, you need to use a hand pump and a siphone tube. Also, you would need to get a fuel storage can and a thin, long screw driver. 

What to do when Filled Unleaded in a Diesel Engine?

Ensure not to turn on your ignition. Also, take your keys from the ignition. Push your vehicle to a vacant place and ask for the assistance of a breakdown cover. You can also ask for help from the petrol station staff. Ensure not to take off your keys from the ignition. This is the easiest and simplest way compared to others. The best thing a motorist can do after putting petrol in a diesel car is to drain it. 

Problems Associated with Putting a Small Amount of Petrol (or the Wrong Fuel) in a Diesel Engine

Even a small amount of petrol in a diesel engine can lead to a variety of problems—both immediate and long-term. One of the primary concerns is damage to the diesel fuel system, particularly the fuel pump, which relies on diesel for lubrication. Without proper lubrication, internal components may wear prematurely or fail altogether.

Over time, continued use of contaminated fuel can lead to engine misfiring, reduced performance, and potentially complete breakdown of the diesel engine. If you’ve added even a small quantity of petrol to a diesel vehicle, it’s important to act promptly and request assistance from qualified personnel to safely drain the fuel system.

What Percentage of Petrol Is Considered Safe?

In most cases, no more than 3% petrol contamination is considered marginally acceptable—though even this is not recommended. Petrol (gasoline) has a much lower cetane rating (typically between 10 and 20) compared to diesel, which can interfere with combustion efficiency in diesel engines.

While small accidental amounts may not immediately destroy an engine, petrol lowers the flash point of diesel fuel, increasing the risk of misfiring and component stress. Moreover, petrol does not provide the same lubricating properties as diesel, making it unsuitable for high-pressure diesel injection systems.

To protect your engine and maintain optimal performance, it’s best to avoid any contamination and ensure that only the correct fuel is used.

Misfuelling

To mix or not to mix diesel with petrol? The answer is not to mix. Mixing the unleaded with diesel could cause a breakdown of engine parts. Misfuelling is also a common mistake that needs to be avoided from time to time. It could cause bigger issues than the other way around.

Wrong Fuel

Putting the wrong fuel to your fuel tank, even a small amount of petrol could lead to damages. If you mistakenly put petrol to your fuel pump or diesel engines, make sure to drain it by a professional – Do not waste time. When you put the wrong fuel to your new car model, draining it is way harder than the other way around. Ensure that you know the different car systems to determine if you actually put petrol in a diesel car. 

Car Engine Injection

Through the injectors and their fine holes, the fuel is being fired into the inlet port or inlet manifold. The fuel pump delivers the fuel from the fuel tank, which is under pressure, to distribute it to one cylinder equally and on time. Injectors are an important part of every car to perform fuel injection. You could purchase it even from the petrol station. The injectors could be found next to the firing line. When the injectors are damaged, it could also cause risks to your engine. Diesel is used to waxing up injectors.

Things to Keep in Mind

• To put the diesel into the car tank, make sure to pour it first into an unleaded fuel can.
• New models of cars these days are equipped with quality and new fuel tank features.
• We advise you to drain your engine when you accidentally pour the wrong fuel to protect yourself from buying a new car or, worse, replacing your engine with a new one. 
• Even if you start your engine after putting in the wrong fuel, you need to fix it before it gets worse.
• When you put the wrong fuel, do not even attempt to start your engine.
• Ensure that you know your vehicle tank capacity.
• More than hundreds of drivers don’t know how to fix misfuelling.
• You may use a knock sensor to help fix some car problems. 
• Diesel before 2001 may be safer compared to now.
• Drain your fuel tank. Call a professional to drain your car engine properly. 
• Staff in a station can drain your engine and refuel it. If you are alone and this mistake happens, you can drain it yourself. You need to drain out the diesel from the tank to start the engine.
• When the engine is fine, drive your vehicle slowly.
• Diesel engines are made from different materials. This is also true in the fuel system. 
• Putting even a small amount of petrol in diesel engines can lead to damages to the entire fuel system.
• Other drivers prefer adding a small amount of petrol to diesel fuel during the winter season.

One may consider putting a sticker or indicator right next to the fuel system.

No one wants to spend money on repairs to their car system. One of the ways to prevent it is to ensure that you are putting the right fuel to your car as your engine may show defects if it receives the wrong fuel. 

If the mistake already happened, it would be great if you would drain it. Draining the system would be the least expensive thing you can do to save your system. You would really have to put diesel into an unleaded fuel tank. 

There are two types of diesel engine systems, which include high pressure injection and common rail injection. A common rail injector system would cost you a lot. Also, to make sure that the common rail injector system is working, note that it depends on lubrication most of the time. 

On the other hand, a high pressure fuel pump is costly compared to other components of the system. Running a high pressure fuel pump with a small amount of petrol can lead to further damages to the system. 

If you still have questions, you could call us for free. If you need help regarding your vehicle engines, you could call your vehicle manufacturer for free. How Can we help you? Call and discuss with us the damage to your tank fuel system. Get a new car quote. 

Subscribe to get the latest updates regarding this topic. Ensure to get a car finance that is designed to meet your needs. Get a new car quote and arrange a test drive to get the proper ways of fixing the damaged engine. Get the latest guides, reviews, and news when you subscribe. 

Also anything extra, you might want to check out video.