Petrol's Xtra-Premium and Power variants vary in India from seller to seller. Octane numbers or octane ratings are much higher than the standard petrol / gasoline ratings. The fuel Octane rating is an indicator of how well inside the engine the fuel can withstand compression.
The extra premium octane number is 91-93, and the standard petrol number is 85-87. The higher the octane number , the greater the engine performance.
Most standard vehicles are equipped to run on 87-octane fuel, but higher octane fuel may be needed for performance vehicles, such as those that use turbocharging or supercharging to push more air into the engine.
The benefit of higher octane fuel is that the heat of compression is harder to ignite, that an engine can be run with higher compression, thereby producing more power. An engine designed for a lower octane fuel does nothing, even if the higher octane level is obtained by additives that have less energy than gasoline, the low octane engine 's output will be decreased.
The use of a standard fuel in a larger engine may lead to poor performance of the vehicle and could degrade its performance. It can also cause the engine to be damaged and your fuel economy would also suffer.
There is not much difference between the number of two octans, so only 3-4 kmpl can increase the mileage.
In short, after the car has driven a few thousand kilometres, extra premium fuel should be used because it includes certain cleaning additives.
But if you have a car with a engine compression ratio of 10 or more ... it's going to run perfectly with regular fuel.
But with additional premium, very high vehicles with a compression ratio can clock their best BHP.