Putting the wrong fuel in your car is a common mistake. It often happens when you are in a hurry, distracted, or driving a different car. But don’t panic: acting fast and knowing what steps to take can keep damage to a minimum. To avoid putting the wrong fuel in your car, always double-check the pump and nozzle before refueling.

Here’s a guide for what to do (and what to avoid) if the incorrect fuel goes into your tank. Misfuelling can be a costly mistake, leading to expensive repairs or engine damage, so it’s crucial to give your full attention when refueling to prevent such errors.

What is Misfuelling?

Misfuelling—putting the wrong fuel in your car—is a very common mistake that can happen to anyone, whether you drive a diesel car or a petrol car. It usually occurs when you’re distracted, in a rush, or unfamiliar with the vehicle. This simple error can have serious consequences for your car’s engine and fuel system, especially if the mixed fuel circulates through the system. Diesel fuel and petrol are designed for different types of engines, and using the wrong fuel can lead to permanent damage if not addressed quickly. If you realise you’ve put the wrong fuel in your car, it’s important to act quickly and seek professional help to prevent further issues. Remember, the sooner you respond, the better your chances of saving your car from costly repairs.

Fuel Types and Risks

There are two main types of fuel used in cars: petrol and diesel. Petrol cars require petrol, while diesel cars are designed to run on diesel fuel. Each fuel type has unique properties that suit specific engine designs. Putting petrol in a diesel car can contaminate the entire fuel system, leading to expensive repairs and potential engine damage. On the other hand, putting diesel in a petrol car can cause the engine to stall or fail to start, as diesel does not ignite properly in a petrol engine. Both scenarios can result in contaminated fuel in your tank and may require the system to be drained and cleaned by a recovery service. Understanding the risks of using the wrong type of fuel in your car is essential to avoid this common mistake and protect your vehicle from unnecessary damage.

Importance of Correct Fuel

Using the correct fuel in your car is vital for keeping your engine and fuel system running smoothly. Diesel fuel acts as a lubricant in diesel engines, helping to reduce friction and wear on moving parts, while petrol fuel is formulated for the needs of petrol engines. Putting the wrong fuel in your car can cause increased friction, damage to the fuel system, and even engine failure. Always double-check the fuel type before filling up—your car’s user manual or a label inside the fuel door will tell you which fuel to use. Since September 2019, fuel pumps have new labels to help you choose the correct fuel: look for ‘E5’ in a circle for petrol and ‘B7’ in a square for diesel. Paying attention at the pump and using the correct fuel will help you avoid costly mistakes and keep your car in top condition.

Step 1: Don’t Start Your Car

This is the most critical rule. If you realise your error while still at the pump, do not turn the ignition or power up the electrics. Starting the engine will push the wrong fuel through the fuel system, which can cause more damage, especially in a diesel engine.

If it is safe to do so, pull your vehicle to a secure location without starting the engine.

Knowing how much fuel was mistakenly added can affect the next steps and the potential for damage.

Step 2: Alert the Station Staff

Let the petrol station staff know what has happened. They have probably seen similar situations before. They can help you move the vehicle to a safe place. They can also assist you in contacting a recovery or service provider.

Petrol station staff are usually ready to offer assistance or advice if you encounter any issues at the station.

Step 3: Contact Your Breakdown or Insurance Provider

Check whether your policy or breakdown cover includes “misfuel assistance” (sometimes called “wrong fuel cover”). If it is included, your car insurance may arrange to drain, flush, and clean your tank. They might even cover some damage costs, but only up to a limit.

It is important to have qualified mechanics assess and repair your vehicle to ensure any issues are properly diagnosed and resolved.

If you’re unsure whether your policy covers this, call them before agreeing to or paying for any work. They can advise you on whether you should authorise repair services or arrange for the service themselves.

Getting Your Car Checked

If you’ve accidentally put the wrong fuel in your car, it’s essential to have your vehicle checked by a professional mechanic as soon as possible. Even if your car seems to be running normally, contaminated fuel can cause hidden damage to the fuel tank, fuel system, and other components. A qualified mechanic can drain the tank, flush the entire fuel system, and replace any damaged parts to prevent further damage. It’s also a good idea to review your car insurance policy to see if misfuelling is covered, as some policies may help with the cost of repairs. Acting quickly and getting your car checked by a professional can save you from more expensive repairs down the line and ensure your vehicle stays safe and reliable.

Why Putting Petrol in a Diesel Car Is Particularly Serious

It’s a more common mistake than you might think to put petrol in your diesel car — petrol nozzles often fit more easily into diesel fuel tanks. The problem? Diesel acts as a lubricant for engine parts, whereas petrol does not. When petrol mixes with diesel and circulates, it acts as a solvent, dissolving the lubricants in the fuel system. This process increases friction between engine components, which can damage important parts like the fuel pump and lead to expensive repairs.

What Happens If You Put Diesel in a Petrol Car

Diesel nozzles are generally larger and won’t fit into many petrol vehicles, but mistakes do still happen. In petrol engines, diesel doesn’t ignite properly, which can lead to ignition failure. Diesel can also foul the spark plugs, causing misfires or engine performance issues. If you catch it early (before starting the engine), a drain-and-flush should usually fix things and prevent serious potential damage.

Tips to Prevent Misfuelling

A few small precautions can help you avoid this stressful mistake:

• Always double-check the pump before filling — take a moment to confirm the correct fuel.

• Consider placing a reminder label inside your fuel cap, especially if you’ve switched vehicles or fuel type recently.

• Diesel owners can buy filler-cup inserts or adapters to physically block petrol nozzles from fitting. These are relatively inexpensive and may save you from an expensive drain.

Putting the wrong fuel in your car can be stressful. However, if you act quickly and follow the right steps, it doesn’t have to be a big problem. Don’t start the engine, inform staff at the petrol station, and call for help or breakdown cover.

There’s no need to worry—professional services are available to resolve misfuelling incidents quickly and efficiently.

If you’re unsure whether your policy protects you in these cases, feel free to reach out — we at its4women.ie would be happy to help you check your car insurance cover and make sure you’re protected.