In a service station, we generally find four types of fuel: unleaded 95 gasoline, unleaded 98 gasoline, diesel, or gaseous fuels such as LPG or LNG. If your vehicle runs on gasoline, the question arises: can we mix unleaded 95 with unleaded 98 without risk?
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The main difference between unleaded 95 and 98 gasoline is the octane number, a measurement that indicates the resistance to the combustion of fuel, when it is compressed in the cylinder of an engine. Unleaded 95 has an octane percentage of 95, and unleaded 98 has 98! The remaining percentage (5% and 2% respectively) corresponds to heptane.
What are the differences between unleaded 95 and unleaded 98?
Unleaded 98 has a higher non-flammability than unleaded 95. This is due to the behavior of hydrocarbons which compose it: octane is more resistant to combustion. Consequently, the higher the octane number, the more gasoline combustion is controlled, and the more efficient the engine.
So, to ensure a better longevity of our vehicle, we should in theory fill up with gasoline with higher octane number, that is to say gasoline of octane 98. However, without- lead 95 is cheaper at the pump, and overconsumption compared to unleaded 98 is estimated to be less than 2%, making it a cheap option popular with drivers.
If your car is classic, the unleaded 95 is most recommended. On the other hand, for heavier or more efficient vehicles, prefer unleaded 98.
What happens if we trade in unleaded 95 and 98 fuels?
No need to worry too much if one day you get it wrong fuel when refueling! You can mix 95 and 98 gasoline without any short-term negative effects.
If the vehicle is operating normally on 95 gasoline, adding 98 octane gasoline will not make any difference in performance. On the other hand, using 95 in a 98 engine will reduce engine performance and may contribute to its long term fouling.
Thus, it is preferable to always keep the same type of gasoline, that recommended by the manufacturer, and not to change it.
New labeling of unleaded 95 and 98 petrol
Since October 2018, new fuel names are mandatory for service stations across Europe: the 28 European countries have devised this ambitious reform plan.
The new system not only uses new names, but also geometric figures to make it easier for us to identify fuel types.
Gasoline-type fuels use circles, diesel-type fuels use squares, and gaseous fuels use diamonds. The name of the fuel will appear inside these circles.
With this new regulation, unleaded 95 and unleaded 98 gasoline both appear as E5. However, to avoid any confusion in the early years, France implemented additional standardization, and the numbers 95 and 98 will always appear at your service station! Thus, you will find unleaded 95 and unleaded 98 under the names “E5 SP95” and “E5 SP98”.
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