What is the octane number?

Have you ever wondered what the petrol rating is? These numbers in the gas pumps? Every time we go to a gas station to fill our car tank, we always choose what octane number to put in. You can see a sticker on the gas pump, with different ratings available at that station, and see the applied rating calculation method in the United States.

In the US, these ratings vary by 87, 89, 91 or 93 octane numbers. Gas gases with higher gas numbers are termed "Racing Gas" and are (1) generally unusual petrol stations and (2) the price is significantly higher than the conventional octane gas. But what is it with?

Octane number is a number that determines the gasoline property to withstand the explosion under high pressure and high temperature conditions in a given range. It does not mean that octane gas 93 is much more efficient than octane 87, such as Dynamite, is much more effective than gun dust. The means of explosion resistance; how hard we can push or compress that gasoline into the engines (taking into account the temperature) before the spark plug ignites without ignition. When this subsequent unwanted condition occurs, it is called ignition, knock, pinging or simple detonation before. Keep in mind that this is an internal combustion engine or an "explosive engine". The detonations are much stronger, faster and more destructive than explosions. Explosions do not give powerful power to the engine.

The higher the octane, the more it will withstand the above situation. The competitor and muscle car often produce a lot of compression and high temperatures between their engines, and therefore the use of very high octane gas is normal in such vehicles.


It is far from proper for gasoline to fire before it means it will cause a lot of trouble in the engine, affecting its performance and disrupting it. Just imagine the gas, break in the compression file, several degrees in front of "Top Dead Center" or TDC. This is not a desirable situation when the plunger moves upward while the explosion is pushed down at the same stroke at the same stroke. Very bad! It results in zeroing because the explosion will not succeed by pushing the plunger because it is still in the top deadlock and will not move down until the point is reached. In addition, they are destroyed in microseconds, which would have mechanical advantages. He rather strokes the plunger rather than pushing it down.

When an explosion occurs, the force is lost in two conditions: first apparent; the explosion is too fast and despite the engine timing, and the second time the knock sensor detects the explosion, it responds from the car (ECU), which delays the ignition timing several times until it detects more detonations. This is the response programmed in ECU software designed to protect the engine from explosion. The down side is to stop the car.


Octane is not a direct measure of gas power. Each gasoline will have similar refining reactions (explosive power) depending on its refinement quality and purity, regardless of which octane number (87, 89, 91, 93, 104, etc.). The difference is that the lower rating gas (87 and 89 octane) burns without burning before the higher temperature gas (91, 93 and higher octane) under the same temperature, pressure and volume conditions without sparks [19659002] Octan Rating Calculation Methods

There are several calculation methods available: RON, MON, PON or AKI.

RON: (Research Octane Number). The most common fuel in Europe, Australia and some other countries. The variable compression engine can be used to measure fuel behavior. The results are compared with other iso-octane fuels compared with other types of fuel having the same number of octane molecules but not identical organic compounds.

MON: (Motor octane number). Specified variable compression engine with preheated fuel, variable ignition timing and higher RPM than RON. This method specifies the determination of fuel behavior on a loaded engine

PON or AKI (octane number or knock index): The method used in the United States and Canada, [R+M] / 2, The wish is the RON number and the MON number, divided by the number 2. In other words, this is the average between the above two methods.


So, due to the fact that RON is always 4-5 points higher than PON or AKI, the conversion rate between American and European octane numbers is approximately the following:

USA (PON) – > Europe (RON)

87 -> 91

89 -> 93

91 -> 95

93 -> 98

Thank you for reading.

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