Petrol in diesel: what to do if refueling is wrong

Enter the gasoline in diesel at the gas station: it may seem absurd, but it is a mistake which can happen to do. Especially if you are in a hurry, or if you have changed your car and type of diet (the force of habit). Inserting petrol instead of diesel is not a mistake to be underestimated, on the contrary, it can lead to rather serious consequences and important damage to the vehicle. The fact remains that, if the mistake has already been made, we must not panic and try to remedy it as soon as possible.


Putting gasoline in the diesel can cause serious damage to the vehicle, for this reason, if you notice the error in time, it is best not to start the engine, but to call a tow truck and have the nearest mechanic take you to empty the tank.

But what exactly happens when you put petrol instead of diesel? Obviously, gasoline and diesel are two different fuels, with different properties and characteristics. Diesel, for example, since it is more oily, has the ability to lubricate injection systems, while petrol is easily flammable at lower temperatures than diesel needs.

Indeed, with higher temperatures and pressures in the cylinders, the serious risk is that of start a fire, with consequent serious damage to pistons, valves, injectors and filters, such as the particulate filter, which is unable to convert the substances present in petrol. It is precisely the passage of petrol over the filter, already at high temperatures, that can cause a fire.


As we have seen, fire can be the most serious risk, which could also compromise our safety. In the combustion chamber, the fuel could ignite rapidly, causing very hot gas emissions at extremely high rates (diesel fuel needs higher temperatures to burn). The risk of fire, as we have anticipated, can also be caused by the FAP (Particulate Filter), because by not converting the unburned gasoline substances, it allows them to reach the catalyst and cause the outbreak of a fire in the enginesubject to a violent thermal discard and consequent and inevitable breakage.

Furthermore, the lack of lubricant, which is not present in petrol and in diesel oil, would cause a injection pump blockleading tototal shutdown of the plantwith serious consequences on valves and pistons.


The hope is that the error will be noticed immediately and that the engine will not start. In this case, it will be much easier to resolve the matter (but still quite expensive).

If, on the other hand, you start the engine and start normally, we would immediately realize that something is wrong. First, the car will proceed in jerkssobbing especially when we press the accelerator, the engine revolutions will be irregularthere will be noises and gods suspicious sounds coming from the hood And thick black smoke would come out of the exhaust pipe.

Rather obvious symptoms that something is wrong. When these first signs appear, the thing to do immediately is stop the engineso as not to aggravate the damage.

We put petrol in the diesel, unfortunately the mistake was made, we can’t go back. As the saying goes, there are no problems, only solutions. And then we think about how to fix it.

There are two cases to be treated:

  • We noticed the mistake in time and we haven’t started the engine yet;
  • We noticed the mistake with the engine already running.

In the first case, we can do nothing but call a tow truck and have the car taken to the nearest workshop mechanics: here we will deal with empty the tank and clean it.

The second case is the most serious, because when we started the engine and pressed the accelerator, the petrol has already entered the circulation and the more time passes, the greater the risk of the engine being destroyed. In the meantime, they register damage to injectors, pump, particulate filterin short, to the power system as a whole. Naturally, it will be necessary to contact a specialized workshop to repair everything, with a significant economic outlay.

If, on the other hand, you notice it almost immediately, we will have to stop and call the tow truck anyway to be taken to the workshop, but the repair work will be less heavy, with petrol purging and replacement of the particulate filter. In fact, when it starts, the injection pump circulates the fuel in the engine and if it stops after a few seconds, the worst can be avoided.

In this second case, however, there may be a remedy if we have put little, very little petrol in the diesel (we are talking about less than 2%, to be sure). We will be able to remedy this dilute the petrol by filling up with diesel (at least twice) without waiting for the tank to be emptied (halfway through the tank is the ideal time), and then repeat this operation about ten times. Even in this eventuality, however, it will be advisable to go to the nearest mechanic and have it checked.


We now come to understand if some beliefs or rumors are true or not. Among these, the most common is that of add oil. We have put gasoline instead of diesel and, as we have seen previously, since diesel is more oily than gasoline and has a lubricating function, it can be thought that adding oil solves the problem.

Obviously, the matter can’t be that simple: in addition to not being oily, the problem is that petrol is highly flammable and since the diesel fuel system works at very high pressures and temperatures, the risk of starting a fire with petrol is very high.

So, No, if you put gas in diesel, adding oil is useless and not a viable remedy.


Another rumor about the introduction of gasoline into diesel concerns the cleaning the injectors. Some false reports report that gasoline can act as an additive in diesel fuel in order to clean the injectors. The hypothesized solution is to fill the tank halfway with petrol and add diesel for the remainder. Obviously, for all that has been written so far, the petrol in the diesel does not serve to clean the injectors, on the contrary, it seriously damages them (and not only them).


So far we have seen what happens if we put gasoline in diesel fuel. And viceversa? What happens if instead we put the diesel in the tank of a gasoline car? The consequences are more or less the same, although it is slightly less serious.

It must be said, however, that, especially today, it is difficult to put diesel in petrol, because the fillers are different and designed so that they only enter the tanks of diesel-fueled cars. In the event that you manage to make the mistake of inserting diesel in petrol, the same speech made above applies. If the quantity of diesel fuel injected is large, then it will be necessary to call the tow truck, contact a mechanical workshop and have the tank emptied and cleaned. If, on the other hand, the quantity is small, or equivalent to a few liters, then just do it two full of petrolthe second of which once you reach the middle of the tank, and repeat the same operation for a few consecutive times.

In fact, diesel in petrol can cause significant damage to the muffler and spark plugs, due to the oil present in this type of fuel, which would flow into the fuel system, soiling and damaging it.

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About Eric Wilson

The variety offered by video games never ceases to amaze him. He loves OutRun's drifting as well as the contemplative walks of Dear Esther. Immersing himself in other worlds is an incomparable feeling for him: he understood it by playing for the first time in Shenmue.

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