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This is What Happens When You Put Diesel in a Gas Engine

Gas engine

What Happens When You Put Diesel in a Gas Engine

What Happens When You Put Diesel in a Gas Engine

The internal combustion engine is a marvel of engineering, powering millions of vehicles worldwide. However, it’s important to understand the specific fuel requirements of different engines. In this article, we will explore what happens when diesel fuel, meant for diesel engines, is mistakenly poured into a gas engine. This common error can lead to severe consequences for both the vehicle and the owner’s wallet.

Gas engine
Gas engine

Fuel Composition and Engine Differences 

Gasoline and diesel fuels have distinct compositions that cater to the specific requirements of their respective engines. Gasoline contains lighter hydrocarbons, whereas diesel fuel is denser, with heavier hydrocarbon chains. Gas engines use a spark plug to ignite the fuel-air mixture, while diesel engines rely on compression for combustion. Mixing up these fuels can have detrimental effects on the engine’s functionality.

Effects on Engine Performance 

When diesel is introduced into a gas engine, several problems arise. Firstly, diesel fuel doesn’t evaporate as easily as gasoline. Gasoline engines rely on the fuel’s evaporation to create a vapour-air mixture that can be ignited by the spark plug. The lack of proper evaporation leads to incomplete combustion, resulting in reduced power output, engine misfires, and poor acceleration.

Secondly, diesel fuel has a lower octane rating compared to gasoline. Octane rating measures a fuel’s resistance to knocking or pre-ignition. Gasoline engines require fuels with higher octane ratings to prevent knocking. Diesel fuel’s lower octane rating can cause knocking in a gas engine, leading to increased stress on internal components and potential engine damage.

Fuel System Complications

Introducing diesel fuel into a gas engine can wreak havoc on the entire fuel system. Gasoline engines have fuel injectors designed specifically for gasoline. Diesel fuel, with its higher viscosity and different combustion properties, can clog or damage the fuel injectors. The fuel filter can also become clogged due to the presence of diesel contaminants, hindering fuel flow and potentially causing engine stalling or failure.

Catalytic Converter and Emissions System Damage 

Gasoline engines equipped with catalytic converters and emissions control systems are highly sensitive to fuel composition. Diesel fuel contains higher sulfur content, which can poison and damage the catalyst in the catalytic converter. This can lead to reduced efficiency and increased emissions, violating environmental regulations and potentially causing the vehicle to fail emission tests.

Repairing the Damage 

If you accidentally put diesel fuel in a gas engine, immediate action is crucial. Do not start the engine, as it may worsen the damage. The best course of action is to have the vehicle towed to a qualified mechanic who can assess the extent of the damage and perform the necessary repairs. This may involve draining the fuel tank, flushing the fuel system, replacing damaged components, and cleaning or replacing the catalytic converter.

Gas engine
Gas engine

Prevention and Safety Measures 

To avoid the costly mistake of misfuelling, follow these precautions:

  1. Pay attention to the fuel pump and select the correct fuel type.
  2. Read the labels and markings on the fuel pump nozzle and fuel cap.
  3. Familiarize yourself with your vehicle’s fuel requirements and features.
  4. If you realize you have misfuelled, do not start the engine and seek professional assistance.

What results from using incorrect fuel?

The effects will occur whether you fill a diesel automobile with gasoline or the other way around. The extent of the effects, however, may vary depending on whether a diesel or gasoline engine is used. The scenarios and their effects are described below.

1. Petrol in a diesel vehicle

In actuality, it’s challenging to get diesel in a petrol vehicle. This is because the fuel filler nozzle on a diesel vehicle typically does not fit in a fuel filler on a petrol vehicle. However, if you accidentally put diesel fuel in a petrol vehicle, it could harm the engine’s internals and fuel lines.

Diesel is a thick fuel, whereas gasoline is thin. As a result, the petrol engine is not built to handle diesel’s characteristics. Because it’s not made to handle the greasy nature of diesel, the fuel filter may clog up if you start a petrol engine with diesel in the fuel tank. 

Further fuel movement could block the fuel injectors if it somehow manages to do so. Due to soot buildup from the gasoline and diesel mixture, the spark plugs may also fail.

Symptoms of diesel and gasoline mixture

  • The clogged fuel filter may prevent fuel from getting to the engine. 
  • It leads to an engine misfire, which causes it to stumble and stall.
  • Additionally, the exhaust pipe may be spewing out a significant amount of white smoke.
  • The engine will eventually stop having any power, and you won’t be able to start it.

2. Gasoline in a diesel vehicle

Given that the petrol dispenser nozzle is smaller and may easily fit into a diesel fuel tank nozzle, the likelihood of filling a diesel vehicle with gasoline is significant. It is also a regrettable situation because using gasoline in a diesel engine can seriously harm the internal parts.

In a diesel engine, the fuel is ignited by compression. Consequently, the fuel enters the engine’s interior. It serves as a lubricant as well. Therefore, if gasoline is added to the engine, the drying effects of the fuel could harm the parts. The fuel injection pump, which depends on the lubricating ability of diesel, may mostly malfunction.

Symptoms of gasoline and diesel mixture

  • As was already noted, it can be challenging to tell whether a diesel car contains gasoline.
  • When you notice black fumes flowing from the exhaust pipe, you probably realize that you made a mistake.
  • The black smoke is caused by unburned fuel.
  • After then, the engine would sputter and lose power.
  • You won’t be able to start the engine after that.

How to Handle Diesel in a Gas Engine

Not to worry. In comparison to pumping gasoline fuel into a diesel engine, which can be much more dangerous, using diesel fuel in a gas engine is by far the superior option.

Let’s imagine you unintentionally put 50% diesel in your gas tank. It’s also conceivable that your car won’t start, in which case you’ll need to have it towed to a mechanic so the tank can be drained.

What you should do is as follows:

  • Estimate the volume of diesel injected into the gas tank. Knowing if you merely added a drop of diesel fuel or whether the tank is now 50% full is useful. 
  • Never attempt to drive the car. Reduce the likelihood of expensive repairs by not operating the car. You may prevent sucking up diesel into the fuel line by not operating the car. Your engine could seize if you try to drive the car with diesel in it, necessitating potentially expensive repairs. Also, this needs to be addressed right away. Too much time spent letting diesel fuel linger can harm the environment much more. 
  • Call a garage. Contact a local garage you trust and explain the situation. They will most likely recommend draining your gas tank. Make arrangements with the garage so that when the tow truck arrives, the tow truck can directly deliver the vehicle to the garage.  
  • Call a tow truck. As soon as you hang up with the garage, reach out to a tow truck company to have your vehicle towed to the garage.

The distinction Between Gasoline and Diesel Fuel

Although gasoline fuel is produced from crude oil, like diesel, it has slightly different additives that alter its composition. Ethanol is most frequently blended with gasoline fuel. The majority of motor gasoline currently sold in the United States, according to the U.S. Energy Information Administration (EIA), contains roughly 10% fuel ethanol by volume.

Despite having a similar chemical structure to gasoline and diesel fuel, there are a few variances between the two. What is diesel fuel, and how is it different from conventional gas? 

  1. Compared to gasoline, diesel fuel is significantly denser. This indicates that more mass is contained inside the same volume. 
  2. A gallon of diesel fuel contains roughly 14 per cent more energy than a gallon of ordinary gasoline because diesel fuel is about 14 per cent heavier. 
  3. The problem is worse if you use ordinary gasoline in a diesel car. Regular gas is not intended to be used in place of diesel fuel since diesel fuel is also regarded as a lubricant, which prevents the fuel injector pump from being adequately lubricated. 
  4. When incorrectly supplied to a diesel vehicle, gasoline detonates earlier, which can lead to engine damage, misfiring, and knocking. This can result in even more expensive repairs.

Paying Attention Pays

The final word? Pay attention when filling up! Avoiding the easy error of using the incorrect fuel can save you a lot of money on repairs and spare you a major hassle related to your car. If you’re unsure if the vehicle you’re driving runs on gas or diesel, consult the owner’s manual or look for a label on the fuel door.


Putting diesel fuel in a gas engine is a mistake that can lead to a range of costly and potentially irreparable damages. From reduced engine performance and fuel system complications to catalytic converter damage, the consequences.

Frequently Asked Questions

What Happens When You Put Diesel in a Gas Engine

1. What happens when you put diesel fuel in a gasoline engine? 

Putting diesel fuel in a gasoline engine can cause misfiring, poor performance, stalling, and smoke due to improper ignition and incomplete combustion.

2. Can putting diesel fuel in a gas engine cause permanent damage? 

Yes, it can. Diesel fuel can damage fuel injectors, spark plugs, catalytic converters, and sensors, potentially leading to expensive repairs or engine rebuilds.

3. What should you do if you accidentally put diesel fuel in a gas engine? 

Do not start the engine. Have the vehicle towed to a professional mechanic who can drain the fuel tank, flush the system, and replace damaged components.

4. Is there a way to prevent putting diesel fuel in a gas engine? 

Double-check the fuel nozzle and pump, ensuring they match your vehicle’s fuel type. Pay attention to fuel grade and type labels to avoid misfuelling.

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