XP100 – India’s first 100 Octane Petrol

Context: Indian Oil Corporation has launched country’s first 100 Octane petrol.

  • Branded as XP100, the premium grade petrol was launched across selected cities
  • The fuel is manufactured at IOC’s Mathura refinery in Uttar Pradesh and supplied at select petrol pumps.


  • Octane ratings are measures of fuel stability.
  • It is a measure of a fuel’s ability to avoid knock.
  • Knock occurs when fuel is prematurely ignited in the engine’s cylinder, which degrades efficiency and can be damaging to the engine.
  • Worldwide, 100 Octane petrol has a niche market for luxury vehicles that demand high performance and is available only in six countries of USA, Germany, Greece, Indonesia, Malaysia and Israel.
  • At most retail stations, three octane grade are offered, 87 (regular), 89 (mid-grade) and 91-93 (premium).
  • The higher the octane number, the more resistant the petrol mixture is to knock.
  • The use of higher octane fuels also enables higher compression ratios, turbocharging, and downsizing/downspeeding—all of which enable greater engine efficiencies and higher performance in modern high end/ performance vehicles.
  • The octane rating is a measure of the resistance of gasoline and other fuels to detonation (engine knocking) in spark-ignition internal combustion engines.
  • High-performance engines typically have higher compression ratios and are therefore more prone to detonation, so they require higher octane fuel. 
  • Petrol, or Gasoline, in technical terms is called Motor Spirit (MS), or Automotive Gasoline.
  • Petrol is normally produced by refineries by the fractional distillation of crude oil, with further treatment including addition of multifunction additives to enhance its Octane rating (number) and other properties.
  • Technically, it is a complex mixture of hydrocarbons that are balanced to deliver a satisfactory engine performance over a wide range of operating conditions.
  • A key parameter for Petrol is the octane number, which is a measure of its resistance to knock.
  • In a spark-ignition engine, the air-fuel mixture gets heated during the compression cycle and is thereafter triggered by the spark plug to burn rapidly, as per the engine design requirements.
  • Higher compression ratios enable the engine to extract more mechanical energy from a given mass of air-fuel mixture, leading to higher thermal efficiency.
  • With regard to the fuel, gasoline engines with higher design compression ratios typically require fuels with a higher octane rating.
  • Use of petrol with lower than prescribed octane number may cause the air-fuel mixture to prematurely self-ignite before the ignition system sparks, with a characteristic “knocking” or “pinging” sound, which is undesirable as it may damage engine components due to higher pressures.
  • Note: A lower-performance engine will not generally perform better with high-octane fuel, since the compression ratio is fixed by the engine design.

Some technical details

  • The octane number of a fuel is measured in a test engine, and is defined by comparison with the mixture of iso-octane and normal heptane which would have the same anti-knocking capacity as the fuel under test: the percentage, by volume, of iso-octane in that mixture is the octane number of the fuel.
  • For example, gasoline with the same knocking characteristics as a mixture of 90% iso-octane and 10% heptane would have an octane rating of 90. Because some fuels are more knock-resistant than iso-octane, the definition has been extended to allow for octane numbers higher than 100.
  • The octane rating of a spark ignition engine fuel is the detonation resistance (anti-knock rating) compared to a mixture of iso-octane (2,2,4-trimethylpentane, an isomer of octane) and n-heptane.
  • By definition, iso-octane is assigned an octane rating of 100 and heptane is assigned an octane rating of zero.
  • An 87-octane gasoline, for example, possesses the same anti-knock rating of a mixture of 87% (by volume) iso-octane and 13% (by volume) n-heptane.
  • This does not mean, however, that the gasoline actually contains these hydrocarbons in these proportions. It simply means that it has the same detonation resistance as the described mixture.
  • Octane rating does not relate to the energy content of the fuel. It is only a measure of the fuel’s tendency to burn rather than explode.


  • In the early 20th century, automotive manufacturers were searching for a chemical that would reduce engine knock.
  • In 1921, automotive engineers working for General Motors in USA discovered that tetraethyl lead (better known as lead) provided octane to gasoline, preventing engine knock.
  • While aromatic hydrocarbons (such as benzene) and alcohols (such as ethanol) were also known octane providers at the time, lead was the preferred choice due to its lower production cost.
  • Leaded gasoline was the predominant fuel type until India began phasing it out in the 2000s because of proven serious health impacts.
  • All fuels marketed for vehicles in India are unleaded.

Do you know about waste recycling?

  • Fuel obtained from plastic waste has high octane rating. It contains no lead and is known as “green fuel”.

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