Accidentally Filled Your Car With Diesel Instead of Petrol? Here's What to Do

Put Diesel in a Petrol Car? Here's What to Do

Accidentally filling a petrol car with diesel can damage its fuel system, but switching off the ignition immediately can help prevent further complications. Do not start the engine, move the vehicle to a safe location and arrange professional assistance to drain and flush the fuel tank. It is an easy mistake to make, especially when drivers are rushing or unfamiliar with a vehicle. However, what you do in the first few minutes can make a significant difference to the repair process and potential costs.

What Happens When Diesel Goes Into a Petrol Car?

Diesel and petrol are different fuels designed for different types of engines. Petrol engines rely on spark plugs to ignite an air-and-fuel mixture, while diesel engines use compression ignition. **Diesel does not burn properly in a petrol engine.** It is thicker and less volatile than petrol, which means the engine may struggle to combust the contaminated fuel correctly. If the engine is started, diesel can coat the spark plugs and contaminate the fuel system. This may cause misfiring, rough idling, excessive exhaust smoke and reduced engine performance. **The longer the engine runs, the greater the risk of complications.** In more serious cases, contaminated components may require cleaning or replacement. The good news is that if you notice the mistake before starting the engine, the problem may be limited to draining and flushing the fuel tank.

What Should You Do Immediately?

If you realise that diesel has been pumped into your petrol car, avoid panicking. Follow these three important steps to minimise the risk of further damage.

1. Do Not Start the Engine

**This is the most important step.** Do not turn the ignition on, press the start button or attempt to drive the vehicle away. Even if you have only pumped a small amount of diesel into the tank, starting the engine can circulate the contaminated fuel through the fuel lines and other components. If you are still at the petrol station, inform the attendant about the mistake immediately.

2. Move the Car to a Safe Location

**Do not drive the vehicle to another parking space.** Instead, put the transmission in neutral and ask the petrol station staff for assistance in pushing it to a safe location, provided it can be done safely. Keep the ignition switched off and follow the station staff's instructions. If the vehicle is blocking a fuel pump, informing the staff will help them manage the situation without putting other motorists at risk.

3. Call for Professional Assistance

**Get the vehicle inspected by a qualified mechanic or wrong-fuel recovery specialist.** The contaminated diesel needs to be removed from the fuel tank before the vehicle is driven again. A professional may need to:

• Drain the contaminated fuel from the tank.
• Flush the fuel tank and relevant fuel lines.
• Inspect the fuel filter and spark plugs.
• Check the fuel injectors and other affected components.
• Refill the vehicle with the correct petrol after confirming that the system is clean.

Depending on the situation, the vehicle may need to be towed to a workshop for further inspection.

What If You Have Already Started Driving?

If you have already started the engine or driven away before noticing the mistake, do not continue your journey. **Pull over somewhere safe and switch off the engine as soon as possible.** Avoid restarting the vehicle, even if it appears to be running normally. Some drivers may not notice anything unusual immediately. However, contaminated fuel can eventually cause several warning signs, including:

• Engine misfiring: The engine may shake or run unevenly.
• Excessive exhaust smoke: You may notice unusual smoke coming from the exhaust.
• Reduced engine power: The vehicle may struggle to accelerate.
• Rough idling: The engine may vibrate or run inconsistently while stationary.
• Engine stalling: The vehicle may suddenly stop running.
• Difficulty restarting: The engine may struggle or fail to start again.

**Tell the mechanic how much diesel entered the tank and approximately how far you drove.** This information can help determine the extent of contamination and which components require inspection.

How Much Does It Cost to Fix Wrong Fuel in Malaysia?

There is no standard repair price for accidentally filling a petrol car with diesel in Malaysia. The final cost depends on the vehicle model, amount of contaminated fuel and whether the engine was started. **A vehicle that has not been started may require a less extensive repair.** In some cases, draining and flushing the fuel tank may be sufficient. However, if the vehicle has been driven, the workshop may need to inspect and clean additional components, including the fuel lines, injectors and spark plugs. The following table explains the possible repair requirements:

**Do not assume that adding more petrol will solve the problem.** Diluting the contaminated fuel is not a reliable substitute for professional draining and inspection. It is also worth contacting your insurance provider to check whether your policy offers any assistance for wrong-fuel incidents. Coverage depends on the individual policy terms.

How Can You Avoid Filling Up With the Wrong Fuel?

Although filling up with the wrong fuel is an avoidable mistake, it can happen when drivers are distracted or unfamiliar with a vehicle. Here are several simple precautions: **1. Check the fuel label before refuelling.** Always read the label on the pump before picking up the nozzle. Do not rely solely on the pump's colour. **2. Know your vehicle's fuel requirements.** Check the owner's manual or fuel-cap label to confirm whether your vehicle uses petrol or diesel. **3. Inform the attendant clearly.** If someone else is refuelling your vehicle, tell them the correct fuel type before they begin. **4. Pay attention during refuelling.** Avoid using your phone or becoming distracted while the vehicle is being filled. **5. Use a reminder near the fuel cap.** A small sticker indicating the correct fuel type can help prevent confusion, especially when sharing a vehicle with family members.

Final Thoughts

Accidentally putting diesel into a petrol car does not automatically mean your engine is ruined. However, switching off the ignition, avoiding further driving and arranging professional fuel-system cleaning are essential steps to prevent additional damage. For more convenient car ownership management, download the Motorist App and access its AutoConcierge chat for motoring questions and vehicle-related assistance.

Frequently Asked Questions

1. What happens if I accidentally put diesel in a petrol car?

Diesel does not combust properly in a petrol engine and can contaminate the fuel system, spark plugs and injectors. This may cause misfiring, excessive smoke, reduced power and engine stalling.

2. Should I start my car after putting diesel in the petrol tank?

No. Do not start the engine or turn on the ignition because this may circulate contaminated fuel through the fuel system.

3. Can I drive my car if I accidentally put a small amount of diesel in it?

No. Even a small amount can contaminate the fuel system. Have the vehicle inspected by a professional before driving it again.

4. What should I do if I have already driven my car after putting diesel in it?

Pull over somewhere safe, switch off the engine and arrange for the vehicle to be towed to a workshop. Do not restart it while waiting for assistance.

5. Can putting diesel in a petrol car damage the engine?

Yes. It can cause combustion problems and contaminate fuel-system components. The extent of damage depends on how much diesel entered the tank and whether the engine was running.

6. How much does it cost to remove diesel from a petrol car in Malaysia?

There is no fixed price because workshop charges depend on the vehicle model, amount of diesel added and extent of contamination. Request a quotation before approving repairs.

7. How long does it take to remove diesel from a petrol tank?

A professional drain and flush may take a few hours, although more complicated cases involving damaged components can take longer.

8. Will adding petrol dilute the diesel in my fuel tank?

Adding petrol is not a reliable solution because it does not remove the contaminated fuel. Professional draining and flushing are safer options.

9. Is putting diesel in a petrol car worse than putting petrol in a diesel car?

Generally, petrol in a diesel vehicle can be more damaging because petrol reduces the lubrication needed by diesel fuel-system components. However, both mistakes require immediate attention.

10. Does car insurance cover accidentally putting the wrong fuel in a vehicle?

It depends on your insurance policy and its exclusions. Contact your insurer to confirm whether wrong-fuel incidents, towing or related repairs are covered.

11. How can I prevent putting the wrong fuel in my car?

Check the fuel label before refuelling, confirm your vehicle's fuel requirements and clearly inform the petrol station attendant of the correct fuel type.

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