It is the octane level that decides the grade of fuel and for mid-grade the level of octane should be eighty-nine. If the octane level is less or more than that, the fuel falls under different categories. If you find that the level of octane is eighty-seven you can fit the fuel in the regular category and if the level is higher and reaches about ninety-one or ninety-two the fuel can be considered under the premium category.
The rating system that has been used to separate it under different categories doesn't decide the power that the fuel generates but the grading system only assures that your engine is not getting a knock or ping. The phenomenon of knock occurs when the mixture of fuel and air ignites at the same time when your car cylinder ignites and it happens because of the compression that is independent of combustion that the spark plug initiates.
The rating system that has been used to separate it under different categories doesn't decide the power that the fuel generates but the grading system only assures that your engine is not getting a knock or ping. The phenomenon of knock occurs when the mixture of fuel and air ignites at the same time when your car cylinder ignites and it happens because of the compression that is independent of combustion that the spark plug initiates.
