When arriving at a service station, the most common thing is that we find four types of fuel. On the one hand, we have the pumps that supply 95 unleaded gasoline and 98 unleaded gasoline (E5 and E10, respectively, in accordance with community regulations) and, on the other, those that offer diesel A and diesel B. This is so since 2008 when super 98 disappeared, a fuel made with potassium additives that in 2001 had replaced leaded super gasoline.
Depending on the engine that equips the car we will have to choose between gasoline or diesel. In this article we are going to refer to the first of them and explain the differences between 95 gasoline and 98 gasoline. We will also see if it is possible to feed a gasoline engine with either of the two varieties and what are the consequences of mixing both fuels.
The figures that identify both fuels correspond to their octane number. This value indicates the resistance to detonation of the fuel when it is compressed inside the cylinder of an engine.
As Repsol explains on his blog, for the combustion process to take place inside the cylinder, the explosion of the gasoline-air mixture must be such that it creates the thrust effect on the piston. The push must be smooth and continuous or else the mechanics of the car would be affected. Therefore, the higher the octane number, the greater the gasoline's anti-knock capacity and better engine performance.
This is the reason why 98 gasoline is usually used in high-performance sports vehicles and 95 gasoline is designed for other vehicles with more conventional mechanics. The composition of the latter limits the emissions of polluting particles and helps to keep the engine clean, explains the RACE in an entry on his blog.
The other differences between these two gasolines are the color and the price. 98 gasoline is a more intense blue color than 95 octane, a factor that makes it easily identifiable. Regarding the amount, 98 octane gasoline is substantially more expensive, around 10 cents per liter, depending on the service station we choose to refuel.
If we always drive the same car, we know in advance the type of gasoline that the engine needs to function. Even so, and especially in the case of regularly driving different vehicles, it is possible to get confused and choose the wrong fuel. If the engine is designed to run on 95 gasoline and we refuel with 98 gasoline, we will not notice any difference in performance. We will only have paid more money so as not to get any extra benefit.
On the contrary, if our car is fed with 98 octane gasoline and we add 95 gasoline, we will notice a reduction in performance and even an increase in consumption.
If we make a mistake when refueling when the tank is not completely empty and we mix two types of gasoline, the error has no major consequences. As we have seen before, if we mix 98 octane gasoline with 95 octane gasoline in a car that runs on the latter gasoline, we will not obtain any benefit. In the reverse case, that is, in a high-performance car that is fed with 98 gasoline, the fuel mixture will cause a reduction in performance.
When we drive a car that is not ours and we do not know if it uses 95 or 98 gasoline, the easiest way to find out for sure is to open the compartment where the tank cap is located. On the inside of the hatch there is a sticker indicating the type of fuel, whether diesel or gasoline, and the corresponding octane number.
