Octane . Also called the octane number , it is called the RON (Research Octane Number). It is a scale that measures the anti-knock capacity of fuel (such as gasoline ) to detonate when it is compressed inside the cylinder of an engine .

The two references that define the scale are linear heptane, which is the hydrocarbon that detonates the most, to which an octane number of 0 is assigned, and 2,2,4-trimethylpentane or isoctane, which detonates little, to which a value of 100. Its usefulness lies in that the efficiency of the engine increases with high compression rates, but only as long as the fuel used supports that compression level without undergoing premature combustion or detonation.


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  • 1 Octane determination
    • 1 RON
    • 2 MON
    • 3 Measurement scale
  • 2 Main problems
  • 3 Improvements in gasoline octane
  • 4 Sources

Octane determination

To determine the anti-knock quality of a gasoline, test runs are carried out on an engine, where two different parameters are obtained:


The Research Octane Number which is represented as RON or simply R and is determined by performing a speed of 600 revolutions per minute (rpm) and at an air inlet temperature of 125 ° F (51.7 ° C)


The Motor Octane Number which is represented as MON or simply M and is obtained by a test run on a machine operated at a speed of 900 revolutions per minute and with an air inlet temperature of 300 ° F (149 ° C).

For commercialization and distribution purposes of gasoline, producers determine the commercial octane, as the average of the research octane numbers (RON) and engine octane (MON), as follows:

Commercial octane number = (RON + MON) / 2

Measurement scale

The anti-knock quality of a gasoline is measured using an arbitrary octane number scale. On this scale, iso-octane hydrocarbons (which is not very detonating) were given an octane number of 100; and to n-heptane (which is very detonating), an octane number of zero.

The gasoline octane determination test is carried out on a special single-cylinder engine, progressively increasing the understanding until the detonations manifest. Subsequently, the engine is run without varying the above understanding, with a mixture of iso-octane and a variable amount of n-heptane, which will represent the octane or octane number of the gasoline for which the test was carried out and which it has, therefore, the same anti-knock performance of the hydrocarbon mixture.

Thus, for example, if a gasoline exhibits anti-knock properties similar to a mixture of 95% iso-octane and 5% n-heptane, it is said to have an octane number of 95.

Main problems

The main problems when using low octane gasoline are the generation of detonations or explosions inside the combustion engines, coupled with a malfunction and low fuel efficiency, when the vehicle is in motion, it causes a high emission of pollutants.

Gasoline octane improvements

Globally, several related technologies have been developed to raise the octane number of gasoline, highlighting the following:

  • Application of new refining technologies, catalytic reforming, isomerization and other processes, which allow obtaining gasoline with high clean octane numbers, that is, without additives. This has led to a significant reduction and even elimination of lead tetraethyl, resulting in better quality gasoline, which meets the ecological protection requirements that have been established worldwide.
  • In parallel, new so-called ecological oxygenated additives have been developed to replace lead tetraethyl (which is highly polluting), such as Methyl-Ter-Butyl-Ether (MTBE), Ter-Amyl-Methyl-Ether (TAME) and Ethyl-Teer-Butyl-Ether (ETBE), among others.
  • These oxygenated additives are added to gasoline to raise their octane number, while providing greater oxygenation, which directly affects more complete combustion and better engine performance.
  • Of these oxygenated additives, those that have had the greatest use worldwide, have been MTBE and TAME, due to their high octane value in the mixture with gasoline, their low vapor pressure and, above all, their high availability. , when produced in plants integrated to the refineries, where the refining raw materials required for its production ( methanolbutanes , butylenes, isobutylenes and isoamylene) are used, with the economic advantages that this represents.


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