27 Jul, 23

The Diesel-Petrol Misfueling Conundrum: A Costly Mistake

Mistakes happen to the best of us, but when it comes to Diesel-Petrol Misfueling your car, it can lead to significant consequences. One of the most common misfuelling blunders occurs when diesel is mistakenly pumped into a gasoline car. The results of such an error can range from mild inconveniences to severe engine damage. In this article, we’ll delve into what happens when you put diesel in a petrol car and the steps to take if you find yourself facing this predicament.

Diesel-Petrol Misfueling

1. The Chemistry Behind the Mix-up

Diesel and petrol have different chemical compositions, leading to distinct combustion properties. Petrol, a highly volatile fuel, ignites easily under lower pressure. On the other hand, diesel requires higher pressure and temperatures to ignite. When diesel is introduced into a petrol car, it can disrupt the fuel-air mixture, affecting the engine’s functionality.

2. Immediate Effects

Upon filling up the tank with diesel, you might not notice anything unusual initially. In some cases, the engine might run for a short distance, but as the diesel makes its way through the fuel system, problems begin to manifest.

3. Difficulties in Ignition

The most apparent issue when diesel is mistakenly used in a petrol car is difficulty starting the engine. Diesel does not vaporise as easily as petrol, and the spark plugs designed for petrol engines might not be able to ignite the diesel mixture effectively.

4. Engine Misfires and Reduced Power

If the engine manages to start with the diesel-petrol mix, it is likely to run poorly. You may experience engine misfires, rough idling, and a noticeable reduction in power and acceleration.

5. Increased Smoke and Emissions

When a petrol engine runs on diesel, it produces more smoke than usual. The exhaust emissions become darker and denser due to incomplete combustion of the fuel mixture, leading to environmental concerns.

6. Potential Damage to Fuel System

Diesel has lubricating properties that petrol lacks. When diesel is used in a petrol engine, it can cause wear and tear on the fuel system components designed to handle lighter fuels. Over time, this can lead to expensive repairs.

7. Fuel Pump and Injector Issues

Diesel’s thicker consistency can put additional strain on the fuel pump and injectors, which are not designed to handle such viscosity. This strain can lead to premature wear, clogging, and eventual failure.

8. Draining and Flushing

If you realise you are misfueling immediately, do not start the engine. Running the car could compound the issues. Instead, call for professional assistance to drain the fuel tank and flush the fuel system thoroughly. Technicians will ensure that any diesel residue is removed to avoid further complications.

9. Repairs and Costs

Depending on how far the diesel has circulated through the fuel system and engine, the cost of repairs can vary. In some cases, a simple drain and flush might suffice, while in severe cases, the fuel pump, injectors, and other components might require replacement, incurring substantial expenses.

10. Preventive Measures

To avoid the misfuelling mishap, always be attentive to the pump. Diesel and petrol nozzles usually have different sizes or shapes, making it harder to insert the wrong one. Additionally, double-check the fuel type recommended for your vehicle in the owner’s manual.


1. What is misfueling?

Misfueling refers to the act of filling a vehicle’s fuel tank with the wrong type of fuel. In the context of diesel-petrol misfueling, it occurs when diesel fuel is mistakenly pumped into a petrol (gasoline) vehicle.

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

Putting diesel in a petrol car can lead to several issues. The diesel’s different chemical composition and combustion properties can cause difficulties in ignition, engine misfires, reduced power, increased smoke emissions, and potential damage to the fuel system components and engine.

3. Can I drive my petrol car after misfueling with diesel?

It is not recommended to drive the car after misfuelling with diesel. Starting the engine and driving the vehicle can exacerbate the issues caused by the wrong fuel and lead to more severe damage. If you realize the mistake, avoid starting the engine and seek professional assistance.

4. How can I tell if I’ve misfueled my petrol car with diesel?

The most apparent sign of misfueling is difficulty starting the engine. If you notice that the engine is struggling to start, running roughly, emitting more smoke than usual, or experiencing a significant loss of power and acceleration, there’s a possibility of misfuelling.

5. What should I do if I’ve misfueled my petrol car with diesel?

If you realize the misfuelling immediately, do not start the engine. Contact a professional roadside assistance service or a mechanic to drain the fuel tank and flush the fuel system thoroughly. This will help prevent further damage and avoid costly repairs.

6. Can I fix the issue myself?

While some automotive enthusiasts may attempt to fix the problem themselves, it is strongly advised to seek professional assistance. Modern cars have complex fuel systems, and attempting to repair or flush them without proper knowledge can lead to additional damage.

7. How much will it cost to repair the damage from diesel-petrol misfueling?

The cost of repairs will depend on the extent of the damage caused by the misfueling. In minor cases, a simple drain and flush might be sufficient, which could cost a few hundred dollars. However, in severe cases where fuel system components or the engine is affected, the repairs can run into thousands of dollars.

8. How can I prevent diesel-petrol misfueling?

To prevent misfuelling, always be vigilant at the pump. Diesel and petrol nozzles usually have different sizes or shapes, making it harder to insert the wrong one. Additionally, double-check the recommended fuel type for your vehicle in the owner’s manual before refuelling.

9. Is diesel-petrol misfueling covered by insurance?

Standard car insurance policies typically do not cover damage resulting from misfuelling. It is considered a driver error, and any repairs required will likely be the driver’s responsibility.

10. Can a one-time misfueling cause permanent damage to my petrol car’s engine?

In most cases, a one-time misfueling event is unlikely to cause permanent damage to the engine. If the issue is addressed promptly and the fuel system is thoroughly flushed, the engine should recover without long-term effects. However, it is essential to avoid repeated misfueling incidents, as multiple occurrences can lead to cumulative damage over time.

Read more: Wrong Fuel In Your Car: What To Do

Remember, if you ever find yourself facing a diesel-petrol misfueling situation, it’s crucial to act quickly and seek professional assistance to minimize the potential damage and avoid costly repairs.


Putting diesel in a petrol car can lead to a series of problems ranging from minor inconveniences to significant engine damage. If you ever find yourself in this situation, seek professional assistance immediately and refrain from starting the engine. Being cautious at the pump and double-checking the recommended fuel type for your vehicle are simple yet effective ways to prevent this costly misfuelling error. Remember, prevention is always better than cure when it comes to fueling your car.

Tags : Diesel-Petrol Misfueling.
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