Watch out! Petrol and diesel also expire

You’ve probably wondered about this at some point. Does petrol and diesel expire? The short answer is yes, but there are many nuances to this, so let us explain how this can happen. We have already explained in another article that it is not advisable to run the fuel tank completely dry, and this has a lot to do with the topic of this article.

Petrol expiry

Petrol has an ignition capacity that allows when it mixes with air and a spark occurs, it ignites. That sudden explosion is what drives an engine. However, the ability of petrol to ignite declines over time, and its efficiency may be lost.

The main cause of this ageing of petrol is exposure to air and light. The tank is not completely airtight, and hydrocarbons escape from it, the gaseous molecules responsible for ignition. This happens very slowly, so it does not pose a risk, but it contributes to losing effectiveness by the time it reaches the engine.

Another reason may be oxidation caused by contact with air and light. Unsaturated compounds turn into polymers, and these can end up clogging the injectors, the pump and other engine components. This happens to a greater extent when there is more air in the tank. In other words, when there is more air than fuel in it, the problem gets worse.

The estimated time for petrol stored in a tank to lose its qualities is between two months and a year, depending on several factors. It is therefore advisable to fill the tank and keep replacing the petrol so that it does not lose its qualities. If the vehicle is going to stand still for a long period, it is advisable to fill the tank so that there is as little air as possible.

In the case of plug-in hybrid models, where it is possible to drive in electric mode, you need to pay closer attention to this. If the combustion engine is used very little, the petrol may lose efficiency and expire in the tank. So it is advisable to keep renewing it and not let it become “old” in the tank.

And what about diesel cars?

Diesel deteriorates much faster than petrol. The hydrocarbons in this fuel evaporate more easily, even if the tank is airtight. Moreover, current fuel has a high percentage of biological elements, biomass. These fungi and bacteria tend to reproduce, which can lead to a serious problem. The biomass can form a kind of sludge that clogs various engine parts. So you should not leave the tank unattended and unfilled for more than three months either.