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Your Car’s Diet- What Does An Octane Number Stand For?

February 16, 2011 by - Automotive Editor

Octane Rating

A driver tends to take care of a car like a mother cares for a child. However, as a mother takes very special care of a child’s nutrition, most drivers overlook this necessity of their beloved car. Your car’s performance depends very much on its diet. And what exactly is that diet? It’s the fuel.

How many times have you been at a fuel station wondering what exactly the difference is between different types of gas available, and what exactly would be the best for your car? It happens a lot. The difference of gasoline is actually judged by its Octane number. The octane number itself is a mystery for most of us. Let us explain a few facts regarding this mysterious rating system.


What exactly is Octane Rating?

The octane number or octane rating defines the anti-knocking ability of the fuel. A higher octane number stands for a better anti-knocking ability. In more technical terms you can say that the octane number depicts the resistance of fuel to self-igniting. Fuel with low octane number is general mini bouncy castle considered low quality and less refined fuel that combusts prematurely. Such premature combustion causes knocking or rattling noise. Not only does it sound disturbing, it can cause severe damage to the engine itself.

How Do They Rate A Fuel?

The octane number for fuel is measured under controlled conditions in a test engine. The fuel to be tested is compared against a mixture of two substances Iso-Octane and Heptane. The percentage of each substance is changed in each blend. The blend which most closely resembles the properties of fuel under the test defines the Octane rating of that fuel. For, instance a fuel has the same anti-knocking properties as of the blend of 80% octane and 20% Heptane; its octane number is 80.

How Makes it Higher Than 100?

Although Octane number defines the percentage of Octane, some elements in fuel may also possess anti-locking abilities which can boost the overall property of that fuel.  Such fuels can show better anti-locking property than 100% Iso-octane and therefore the Octane number is higher than 100.  Alcoholic fuels used in racing cars have a higher Octane number. Some additive such as lead can also improve the anti-knocking property of the fuel and hence the octane number.

What Is RON and MON?

RON and MON are two different methods of Octane rating with only a slight difference. As we see it, it is just another way to confuse Americans travelling to Europe and vice versa. In Europe, RON is a common method used for rating. However, in the US a more realistic method is used for rating. It’s sometimes referred to as AKI Anti Knock Index. It shows the average of RON and MON and is generally 5 to 8 points lower than RON.

Which One Is Better For Your Car?

Typically, the octane ratings are defined by car manufacturers. Newer cars need fuel with a high octane number. However, the old ones usually require lower octane fuel. Using low octane fuel in new engines can cause great damage. On the other hand using hi-octane fuel in old engines probably won’t create much of a difference.

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