What Happens When You Put Diesel in a Petrol Car?

  • Wrong Fuel in Car Consequences
  • How to Fix Misfuelling Problem
  • FAQs

Petrol and diesel are the two types of most commonly used automotive fuels in the UAE. They have very different chemical compositions and cannot replace each other. The type of fuel used in a car helps the engine perform and impacts its longevity, preventing wear and tear. Owing to all these performance and longevity-related factors, a car should always be run on the correct fuel. 

That said, what happens when someone accidentally puts diesel in a petrol car or vice versa? To find out, let’s understand the consequences and precautions to take in case of incorrect refuelling.

What If You Put Diesel in a Petrol Car: Misfuelling and Its Impact on Engines

Exploring the diesel in petrol car consequences
Using the wrong fuel type can clog spark plugs and other key components

Whether you have filled diesel in a petrol car or vice versa, the consequences can be pretty serious. If the mistake isn’t rectified timely, it can lead to engine damage. Let’s find out more about the two misfuelling scenarios.

Diesel in Petrol Car Consequences

The very first thing to avoid misfuelling is noticing the size of the nozzle. The nozzle of a car’s petrol tank is noticeably smaller than a diesel dispenser’s nozzle. Nevertheless, in case a petrol car gets filled with diesel, the chances of mechanical damage start building up. Petrol is a much more refined form of fuel than diesel. It is ignited by a chain of reactions in spark plugs. 

If a petrol car is started with the wrong fuel in its tank, it can clog spark plugs and the fuel system. The fuel filters that are not meant for diesel’s greasy properties will be among the first few parts to be affected. Misfueling can also lead to car engine misfires. Misfiring is often followed by a heavy amount of discoloured car exhaust smoke, which can be a critical sign of engine damage.

Petrol in Diesel Car Consequences

Unlike petrol engine functioning, diesel engines work by compressing the fuel to ignite. The fuel is then pushed in to lubricate the critical internal components of a car’s engine compartment. However, in case of misfuelling, the problem starts here. If petrol is circulated throughout the integral parts of the diesel engine, it would be hard to get rid of it.

Since petrol has less viscosity and different chemical properties than diesel, the car’s performance becomes unstable. The most concerning part is that it takes time to show misfuelling signs in diesel cars. Consequently, by that time, black smoke would probably start blowing out through the car’s exhaust system, while its movement gets sluggishly.

Petrol in a Diesel Car or Vice Versa: How to Fix It

How to Fix Putting Diesel in a Petrol car
Here’s what to do if you put the wrong fuel in your car

It is important to handle the wrong fuel in car consequences with extreme care to prevent diesel contamination in a petrol car and vice versa. Here’s what you can do, depending on the misfuelling situation.

  • If the fuel tank is filled up with diesel for under 5% of its total capacity, fill up the rest with petrol and drive the vehicle normally. Diesel can mix with petrol and cause no harm in this case. That said, it is recommended to completely drain the diesel from the tank to avoid any fuel contamination risks.
  • In a case where the amount of diesel exceeds 5% of the tank’s capacity, do not crank the engine. Instead, call a roadside assistance company in the UAE. Get it towed to the nearest workshop. Make sure to follow these tips to safely tow a car. The diesel should be drained entirely. Make sure to drain while flushing the fuel tank. Once the wrong fuel is flushed and cleaned thoroughly, fill it up with petrol again and everything will be good to go.
  • However, in the case of having petrol in a diesel car tank, do not turn the engine on at all. Due to low viscosity, even a very low amount of petrol can cause serious problems to engine parts that are not meant to run on it.
  • The worst-case scenario would be realising the refuelling mistake after driving the car for some time. Stop the car immediately and turn the engine off. The car should be towed to the nearest workshop. Besides getting rid of the wrong fuel, get the fuel filter changed as a precautionary measure. 
  • To effectively tackle the misfuelling problem in a diesel car, clean the fuel lines as well as the injector. Go for a well-reviewed fuel injector cleaner available among a variety of other used car accessories and parts for sale in the UAE
  • Moreover, to avoid misfuelling incidents, make sure to be well aware of all the differences of a petrol vs diesel engine.

Signs of Wrong Fuel in a Car

Watch out for these signs of Petrol car engine damage from diesel
Here are common symptoms of Diesel contamination in petrol car or vice versa

The sooner the misfuelling mistake is realised, the better. Watch out for these symptoms of putting the wrong fuel in a car

  • Engine Misfire: If you experience irregular engine firing or jerking during acceleration, it can be because of the wrong fuel type. It is mainly because of the disrupted combustion process. Engine misfiring is one of the key diesel in petrol car symptoms or vice versa.
  • Excessive Smoke: An unusual amount of smoke, especially dark or black exhaust. This is another common sign of using the wrong fuel in the car.
  • Loud Knocking Sound: An incorrect fuel running through the engine has a high impact on the combustion process. As a result, the engine would start producing a high knocking sound.
  • Difficulty Starting the Engine: Using the incorrect fuel can lead to difficulty starting the engine, as it affects the ignition process. This problem can also occur with a car that has not been used for months. Here are some useful tips for starting after a long time.
  • Engine Stalling or Loss of Power: Wrong fuel can also be one of the reasons why your car engine keeps stalling. Moreover, misfueling can result in a noticeable loss of power while driving, indicating a disruption in the fuel delivery system.


What happens if you put diesel in a petrol car?

If diesel is mistakenly added to a petrol car, it can lead to engine damage. Diesel, being less refined, can clog spark plugs and fuel filters while causing engine misfires. The visible sign of these problems is discoloured exhaust smoke.

What happens if you put petrol in a diesel car?

When petrol is added to a diesel car, the lighter viscosity of petrol can lead to unstable performance. Signs may not be immediately apparent, but over time, the engine may produce black smoke and the vehicle’s movement can become sluggish.

How far can you drive with petrol in a diesel car?

The answer is a definitive ‘no’. A diesel car should not be driven with petrol in its tank. It can cause severe damage to the car’s mechanical internals.

How much is the cost of repairing a misfuelled petrol vehicle?

The repairing cost of a misfuelled car may depend on its make and model, as well as the intensity of the damage. To get an estimate, you can head over to these popular car garages in Dubai or your respective emirate.

These were some of the potential misfuelling scenarios, entailing problems and their quick solutions. To avoid such costly mistakes, make sure to be aware of the common car fuel myths. 

Whether you are looking for a new or a used car for sale in the UAE, beware of its fueling, oiling and fluid requirements. Refer to the car owner’s manual for all the necessary instructions.

For more tips on draining diesel from a petrol car and other mechanical problems, stay connected to the dubizzle auto blog.