Understanding the Impact of Petrol in Diesel Car Engines

Fuel Doctor
Dec 16, 2024
3 min read

Driving a diesel vehicle offers various benefits, including better fuel efficiency and durability. However, mistakes can happen, and one common mishap is filling a diesel car with petrol. This can have serious consequences for the engine and vehicle performance. In this article, we’ll explore what happens when petrol is introduced into a diesel engine, focusing on scenarios such as 20 litres of petrol in diesel car, and provide guidance on what to do if this occurs.

How Petrol Affects Diesel Engines

Diesel engines are designed to operate with fuel that has a high lubricity and low volatility. Diesel fuel lubricates the engine components and enables the combustion process that powers the vehicle. When petrol, a less viscous and more volatile fuel, is introduced into a diesel system, it disrupts this process.

Key Effects of Petrol in Diesel Car Engines:

Reduced Lubrication
Diesel relies on its lubricating properties to prevent wear and tear in engine components. Petrol, on the other hand, lacks this quality. Mixing petrol with diesel dilutes the lubrication, causing premature wear on fuel injectors, pumps, and other key components.
Increased Risk of Damage
Petrol's lower flash point can lead to uncontrolled combustion within the engine. This creates excessive heat and pressure, which can damage the pistons, seals, and other parts of the engine.
Fuel System Contamination
Diesel and petrol don’t mix well chemically. When 20 litres of petrol in diesel car enters the tank, it compromises the integrity of the fuel system, potentially clogging filters and causing long-term issues.

Symptoms of Petrol in a Diesel Engine

Spotting the signs of contamination early can prevent extensive damage. Here are common indicators that petrol may have been mistakenly added to a diesel car:

Difficulty Starting the Engine: The engine may struggle to ignite due to improper combustion.
Unusual Noise: A knocking or pinging sound might occur due to misfires.
Excessive Smoke: Petrol-diesel mixtures can produce black or white smoke from the exhaust.
Loss of Power: The engine may experience reduced performance, making it harder to accelerate or maintain speed.

What Happens When You Add 20 Litres of Petrol in Diesel Car?

The amount of petrol added to a diesel engine significantly influences the severity of the damage. If 20 litres of petrol in diesel car is mistakenly added, it constitutes a substantial portion of the fuel tank. This can lead to:

Immediate Engine Misfires
The engine may misfire or fail to start due to insufficient lubrication and improper combustion.
Accelerated Component Wear
High volumes of petrol accelerate the wear on injectors, fuel pumps, and other parts. If left unaddressed, this can result in complete engine failure.
Costly Repairs
A mixture this large often necessitates draining the fuel tank, cleaning the fuel lines, and replacing damaged parts a potentially expensive process.

Steps to Take If You’ve Added Petrol to a Diesel Car

Mistakenly filling your diesel car with petrol can be stressful, but prompt action can minimize the damage. Here’s what to do:

1. Do Not Start the Engine

Turning the ignition circulates the petrol-diesel mixture through the system, increasing the risk of damage. If you realize the mistake before starting the car, leave the engine off.

2. Call for Assistance

Professional services are essential for safely draining the fuel tank and cleaning the system. Mobile fuel drain specialists can often address the issue on-site.

3. Replace Damaged Components

If the engine has already run on the contaminated fuel, it’s crucial to inspect and replace any damaged parts, such as injectors or filters.

4. Refill with Diesel

Once the tank is cleaned, refill it with high-quality diesel to restore proper engine performance.

Preventing Fuel Contamination

To avoid putting petrol in diesel car engines, it’s essential to stay vigilant at the pump. Consider these tips:

Check Twice: Always verify the fuel pump nozzle before refueling. Diesel nozzles are typically larger and marked in black or green.
Install a Diesel Cap: Specialized fuel caps are available to prevent accidental petrol filling.
Be Cautious in Rental Cars: Familiarize yourself with the fuel type of unfamiliar vehicles.

Why Acting Quickly Matters

The impact of petrol in diesel car engines grows worse the longer the issue is left unresolved. Acting quickly minimizes the potential for lasting damage and ensures the longevity of your vehicle.

Environmental Considerations

Improper handling of fuel spills or contaminated fuel disposal can harm the environment. Always use authorized services to manage fuel-related issues responsibly.

Conclusion

Accidentally adding petrol to a diesel car is a costly mistake, but with immediate action and professional assistance, the damage can often be mitigated. Always double-check the fuel type at the pump and consider preventive measures to avoid such errors. Whether it’s 20 litres of petrol in diesel car or a smaller amount, the steps outlined above can help address the problem effectively.