It’s a mistake that can happen to anyone: using the wrong fuel in our car. Maybe you overslept, missed your morning coffee, and rushed to work, grabbing the wrong pump at the station. Or perhaps you borrowed your partner’s car and unintentionally filled it with petrol instead of diesel.
Regardless of the reason for misfuelling, it’s crucial to know what steps to take when it occurs. Remember, you’re not the only one facing this situation. While there isn’t an exact number of how many people make this mistake each year, it’s common enough in Australia that there are businesses specifically created to address the issue.
But what about the impact on your finances?
Especially when there are ways to prevent it. The following tips can help you avoid finding yourself in that inconvenient situation and engaging in awkward small talk with a tow truck driver all the way home.
But let’s get to know our petrol first.
What’s the difference between regular unleaded and premium unleaded petrol?
In Australia, when it comes to fueling up your vehicle, you’re likely to encounter two main types of petrol at the pump: regular unleaded and premium unleaded. These two options might leave you wondering, “What’s the difference, and which one should I choose?” Let’s break it down in simple terms.
Regular unleaded petrol, often referred to as just “unleaded,” is the standard fuel option available at most service stations. It’s the go-to choice for many drivers because it’s more budget-friendly. The key characteristic of regular unleaded is its lower octane rating compared to premium unleaded.
Now, let’s talk about octane rating. According to this, octane is a measure of a fuel’s resistance to knocking or pinging in your engine. Knocking occurs when the fuel-air mixture ignites before it’s supposed to, causing undesirable vibrations and potential damage to your engine. The octane rating indicates how well the petrol can resist this premature ignition.

On the other hand, premium unleaded petrol has a higher octane rating than regular unleaded. This means it offers better resistance to knocking, providing smoother and more efficient engine performance. While it comes at a higher price, some vehicles, especially those with high-performance engines, benefit from the improved combustion characteristics of premium unleaded.
In the Australian context, many everyday cars run perfectly fine on regular unleaded petrol. Most manufacturers design their vehicles to perform optimally with this standard fuel. However, some high-performance or luxury vehicles might be explicitly designed to take advantage of the higher octane in premium unleaded, resulting in enhanced power and efficiency.
When deciding between regular and premium unleaded, consider your vehicle’s specifications and the manufacturer’s recommendations. Check your owner’s manual or consult with your car dealer to determine the optimal fuel for your car. While using premium unleaded in a car designed for regular unleaded won’t harm the engine, it might not provide any significant benefits either.
It’s worth noting that the choice between regular and premium unleaded petrol is also influenced by your driving habits and priorities. If you’re mainly using your car for daily commuting and errands, regular unleaded is likely sufficient. On the other hand, if you have a high-performance vehicle and enjoy spirited driving, the slightly higher cost of premium unleaded may be justified for the potential performance gains.
What to do if you put the wrong petrol in your car?
Putting the wrong type of petrol in your car can happen to the best of us (except those who already migrated to EV cars). Whether it’s a momentary lapse of attention or confusion at the pump, filling up with the incorrect fuel is a common mistake. If you find yourself in this unfortunate situation, don’t panic; there are steps you can take to minimize potential damage and get back on the road.

The first and most crucial step is to avoid starting your engine. Starting the car could circulate the incorrect fuel through the system, leading to more extensive damage. Instead, shift your vehicle into neutral and push it to a driveway or a safe location if possible. If you’re unable to move the car, contact roadside assistance for professional help.
Next, inform the petrol station staff about the mistake. They may be able to assist you or provide guidance on the next steps. In Australia, most service stations have procedures in place to handle such situations, including draining the tank and flushing the fuel system.
If you realize your mistake before leaving the petrol station, the staff may be able to immediately assist you in draining the tank and replacing the incorrect fuel with the right one. This quick action minimizes the risk of damage to your vehicle.
If you’ve already left the petrol station, contact a professional towing service to take your car to a mechanic. Attempting to drive your vehicle with the wrong fuel can lead to severe engine damage and potentially costly repairs.
Once at the mechanic, they will assess the situation and determine the extent of the damage. In some cases, simply draining the tank and flushing the fuel system may be sufficient. However, if the incorrect fuel has caused significant damage, repairs may be necessary.
It’s essential to be aware that repairing a car that has been fueled with the wrong petrol can be expensive, and the cost will depend on the extent of the damage. Insurance policies may not cover such incidents, so prevention is key.
To avoid putting the wrong petrol in your car, double-check the pump and fuel type before filling up. Take a moment to read the labels and confirm that you’re using the correct nozzle. If you’re driving multiple vehicles with different fuel requirements, make a mental note of the correct fuel for each.
What would happen if I used the wrong petrol in my car?
Using the wrong fuel in your car can lead to significant damage, resulting in costly repairs. Diesel and petrol cars are designed differently to run on their respective fuel types, so misfuelling can cause problems in how the engine operates.
Common Signs
If you don’t realize immediately that you’ve used the wrong fuel, there are signs that can indicate the mistake:
- Difficulty starting the car
- Rough driving experience
- Smoke coming from the engine and excessive exhaust smoke
- Complete loss of power

Petrol in a Diesel Car
Using petrol in a diesel car is more problematic than the reverse situation. Diesel acts as a lubricant in the car, ensuring the fuel pump works correctly. Petrol, on the other hand, does not serve as a lubricant in a diesel engine. This lack of lubrication causes parts inside the diesel engine to rub against each other, leading to damage.
The longer the car runs with petrol instead of diesel, the more severe the issues become. Continuous use of petrol in a diesel car exacerbates the damage, impacting the engine’s performance and potentially causing extensive harm to internal components. It’s essential to address misfuelling as soon as possible to minimize the negative effects on your vehicle.
Diesel in a Petrol Car
Putting diesel in a petrol car isn’t as damaging as the reverse situation, but it’s still not recommended. Petrol cars are designed for petrol, and adding diesel can lead to issues like clogging spark plugs and the fuel system, preventing the engine from starting.
How to fix misfuelling?
To fix the problem, the fuel needs to be drained from the tank, and certain parts may need replacement. This could involve the injector, fuel rail, fuel pump, or any other component that came into contact with the wrong fuel. Generally, diesel systems that had petrol run through them might require more extensive repairs. A licensed mechanic can identify and diagnose the problem, determining the necessary repairs or replacements.
How much does it cost to fix the wrong fuelling?
The cost of repairing the engine and fuel system depends on the damage caused by the wrong fuel. Factors like the type of car, engine size, and whether the engine was started with the wrong fuel impact the price. For minor repairs and fuel disposal, the cost can range from $200 to $300. However, if the engine sustained severe damage from driving with the wrong fuel, the repair costs can skyrocket to as much as $9000. It’s crucial to address the issue promptly to minimize repair expenses and get your vehicle back on the road.








