Petrol Octane Ratings: Which is The Right Fuel For Your Vehicle?

Gasoline or Petrol is the primary fuel used for powering engines that rely on spark ignition. This fuel is extracted from petroleum oil or crude oil mainly by distillation process. This Gasoline or petrol majorly consists of two major components viz. iso-octane and heptane. In a typical spark-ignition engine, if the fuel is not according to the right octane rating, the fuel entering the combustion chamber in the form of air-fuel mixture will not burn completely and these unburnt pockets of air fuel mixture remaining will self-ignite under excessive pressure and create an excess load on engine components. This phenomenon is known as knocking. Octane rating of petrol is in inverse proportion to the probability of knocking. Thus, higher the Octane rating, the chances of knocking are lower. Octane rating or octane number of petrol is the comparison between percentage by volume of iso-octane and heptane. When we say that the octane number of unleaded petrol in India is 91, we mean to say that if the fuel was a pure mixture of iso-octane and heptane, 91% of iso-octane and 9% of heptane is present in the fuel. The Octane rating preference of any engine also depends on its compression ratio. Higher compression engines require higher octane fuel to minimize knocking.

Petrol grades available in India:

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In accordance with the Bharat Stage 3 vehicle emission norms, the minimum octane rating for petrol in India has increased from 88 to 91. Thus, prior to BS3 norms, petrol in India was classified into unleaded petrol at 88 octane rating and premium petrol at 91 octane rating. As on today, petrol in India is classified as follows:

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• Unleaded petrol- 91 Octane petrol without additives. All the vehicles manufactured after 2010 are perfectly compatible with this fuel.
• Premium fuels: viz. Speed, Power, Extra Premium and V-Power are similar in octane rating to unleaded petrol. These fuels have detergent additives for cleaning the fuel system and insides of the engine. We must note that the effects of these fuels can be seen only after prolonged use.
• High Octane petrol: Different manufacturers provide petrol of varying octane ratings in India. BPCL offers Speed 97, which as the name suggests is their 97 Octane petrol variant. HPCL offers poWer99 which is their 99 Octane petrol variant and IOCL has xp100, their 100 Octane petrol variant. These higher-octane petrol options do not have any better effects on our average vehicles in comparison with normal unleaded petrol. Although these fuels exist in the market majorly for vehicles with higher compression ratio engines, any one of us can enjoy a tankful of it during those days when we feel like splurging a bit on fuel.