I put the wrong fuel in my car
Created by Tiago Fernandes at Monday, 3 February 2025
Refueling your car is a more common problem than you might think. A moment of distraction can lead to filling up with the wrong fuel, which can have serious consequences for the engine. But calm down! If you realize your mistake in time, there are ways to minimize the damage.
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What to do if you've added the wrong fuel
If you notice the error while still at the fuel pump, follow these steps immediately:
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If you haven't started the engine yet: |
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If you've already started the engine: |
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“I don't really remember...”
If you're not sure whether you've made a mistake when filling up, there are some signs that can indicate it:
Difficulty starting the car - If the wrong fuel has entered the system, the engine may not start or may take a long time to start. |
Loss of power or engine hiccups - The engine may choke or lose power when accelerating. |
Excessive exhaust smoke - If you notice more smoke than usual or a strange smell, it could be an indication. |
Warning lights on the dashboard - Some cars can detect combustion faults and trigger an engine or injection warning. |
Unusual smell - If you smell something unusual in the fuel or exhaust gases, it could be a sign of a wrong mixture. |
If you notice one or more of these signs immediately after filling up, stop immediately and confirm on the invoice the type of fuel that was used. If there is immediate confirmation that you weren't supposed to use that fuel, follow the procedures above.
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What if I only add a little of the wrong fuel?
Many people think that if they put in just a few liters, there's no problem. But it depends on the amount and type of wrong fuel you put in:
If it's less than 5% of the deposit, in some cases it may not cause immediate problems, but it is not advisable to risk it. |
If it's a larger amount, the ideal is not to start the car and drain the tank before the fuel circulates in the engine. |
For gasoline in a diesel engine, Even small amounts can be harmful because gasoline reduces lubrication in the injection system. |
If in doubt, the safest thing to do is always to drain the incorrect fuel.
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Petrol in Diesel or Diesel in Petrol
Is it worse to mix gasoline in a diesel car or diesel in a gasoline car?
Both mistakes are serious, but they have different impacts:
Petrol in a diesel car - Very dangerous! |
This is the worst mistake of the two. Petrol is much thinner and more flammable than diesel and has detergent properties that can damage the diesel engine's lubrication systems. In addition, the fuel pump and injectors of a diesel engine depend on diesel for lubrication, and gasoline can cause irreversible damage to these components. |
Possible consequences:
Damage to the injection pump and injectors.
Misfires and loss of power.
Risk of overheating and engine damage.
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Diesel in a gasoline car - Less serious, but still problematic! |
If you put diesel in a gasoline car, combustion becomes much less efficient, causing engine failure and excessive smoke. However, most gasoline cars can't even run properly with diesel in the system, because the injectors and spark plugs aren't prepared for this type of fuel. |
Possible consequences:
The engine may not start or may run irregularly.
Excessive smoke and residue deposits in the cylinders.
Possible clogging of the injection system.
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How does the process of draining the wrong fuel work?
If you've filled up with the wrong fuel and still haven't started the engine, the solution is to empty the tank and clean the fuel system. Here's what happens:
Draining the tank - The fuel is removed via a suction system.
Cleaning the injection system - If the engine has been started, it may be necessary to clean the injectors and fuel pump.
Replacing the fuel filter - In some cases, it may be necessary to change the filter to avoid residues of the wrong fuel.
If the engine has run on the wrong fuel, the damage can be more serious and the repair may involve replacing parts such as the injectors or the fuel pump.
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How can this mistake be avoided in the future?
Always read the label on the pump before filling up. One second's attention can prevent a major problem. |
Put a sticker on the tank with the correct type of fuel. Some workshops offer this for free. |
If it's a new or rental car, always check before filling up. It's easy to make mistakes when you're not used to another vehicle. |
Avoids distractions when filling up. Fiddling with your phone or chatting can lead to mistakes. |
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Filling up your car wrong can be costly, but acting quickly can prevent major damage. If you've filled up with the wrong fuel, the golden rule is not to start the engine and seek assistance as soon as possible. If you have, turn it off immediately and take the car to a garage.
Translated with DeepL.com
