Regular Fuel vs Premium Fuel- Should you Use High Octane Fuel For Your Car?

We are back with another interesting and popular theme in this section of Automobile Technology content. This time around, we answer the question that many of the daily car users face. Should you use premium fuel for your car? We are sure you must have seen a ton of advertisements about the benefits of using premium or high octane fuel in your cars and you must’ve thought about whether or not your car requires it or not. Well, we shall try to understand the functioning of the engine and what different kinds of fuels do to the characteristics of an engine. Only then you can know if your car’s engine needs the higher octane fuel or not. So, without wasting any more time, let us dive into this interesting topic and try to come up with a logical answer.

Also read: Indian Oil launches 100 Octane Fuel in India at Rs 160 per litre!


What is Engine Knock?

Well, to understand the need of using high octane fuel, we must first make ourselves aware of the phenomenon known as engine knock. We have discussed, at great length, about the engine knock in one of our previous articles on Engine Knock and its consequences on the engine. We suggest you go through that to gain a complete understanding of the topic. However, for the purpose of understanding today’s theme, we will try to understand the phenomenon of engine knock very briefly.

Also read: What is engine braking? How does cooling system work in a car?

In a four-stroke engine, the second stroke is referred to as the compression stroke. During this stroke, the fuel and air are mixed together thoroughly inside the cylinder of the engine and compressed to be ignited by the spark plug. It must be noted here that we are talking about petrol engines. At the end of the compression stroke, the spark plug ignites the air-fuel mixture and the chemical explosion takes place. This is actually what causes the piston to move downwards, resulting in the third stroke of the engine, known as the power stroke. The chemical energy of the fuel is converted into heat energy which is used to propel the car forward.

Also read: What are Catalytic Converters? How do these reduce emissions?

Now, a lot of characteristics of a car/engine depend upon when exactly is this air-fuel mixture is ignited. If it is ignited at a later stage, we lose some power because the piston has already started moving downward and the explosion loses its efficiency. If however, we ignite the air-fuel mixture early, there is a danger that the high temperature and pressure in some pockets of the cylinder of the engine might cause the air-fuel mixture to burn pre-maturely, befor the spark plug has been ignited. This causes a lot of damage to the engine because of the unwanted and untimely combustion. This causes a specific sound in the engine and can even cause damage to the engine components. We have to avoid this at any cost.

Also read: Types of Alternate Fuels – Ethanol, CNG, Bio-diesel, LPG and more!

What is Octane Number?

Octane number is very common terminology used to determine the resistance of the fuel to self-detonate. Like we explained in the previous paragraph, to avoid the self-detonation characteristics of petrol is of utmost importance. Hence, we use fuels that have higher octane numbers. This allows for a bit advanced timing of the ignition process and hence more power can be produced. If more power is not the requirement, then the engine can also turn out to be more fuel-efficient. Either way, advancing the ignition timing has a ton of benefits for the engine either in terms of faster acceleration times or better mileage. Hence, some car manufacturers recommend using higher octane fuels.

Also read: How do power and torque overcome the resistive forces in a car?

Essentially, the octane number is determined by the different chemical compositions of the fuel. The petrol and diesel fuels are essentially hydrocarbons that are arranged in different arrangements. Depending upon the chemical compositions the fuels are categorized as high octane, mid octane or low octane fuels. The types of low octane fuel in India are 87 octane fuel. Mid-octane fuel can be considered 89-91 octane fuel and high octane fuel can be considered with octane number above 91. Recently, Indian oil launched the 100 Octane fuel in India at a cost of Rs 160 per litre. These are extremely expensive fuels and must only be used if your car manufacturer recommends them.

Also read: How does combustion work? What are fuel injectors and spark plugs?

Should you use high octane fuel in your car?

Whenever you buy a new car, the car manufacturer makes it clear on the user manual, what kind of fuel will provide the best results for your engine. The point of it is that the engineers have already calibrated and designed the engine to offer the perfect balance between power, fuel economy, emissions and anti-knocking properties. Therefore, if your car manufacturer suggests using regular fuel, then even if you use premium fuel, your engine will not be able to take advantage of that fuel. Essentially, the fuel doesn’t do anything by itself. The engine needs to recognize the high octane fuel and change the ignition timings accordingly to reap the benefits of using higher octane fuel. However, if the car manufacturers have not built the engine for use with high octane fuel, then there is no point in using it either. It is just a waste of money.

Also read: How does OBD (On-Board Diagnostics) work?

On the other hand, if the car manufacturer suggests using high octane fuel only, then it is for the performance aspect of the car. You will see that many sports or performance cars use higher octane fuels to generate more power. This is because the engine recognizes the type of fuel and advances the ignition timings automatically. However, it must be noted that even if you use regular fuel, the engine will not get affected negatively at all. Only the performance aspect or the power output of the engine may be affected. But using higher octane fuel in regular cars certainly doesn’t offer any benefits.

We hope you enjoyed this article and if you want to learn more about such complex issues in a simple language, do head to the Automobile Technology section of Car Blog India, where we cover many such topics to quest your thirst for understanding complex technical phenomena in simple words.

Also read: Types of ignition systems – Spark, Compression, HCCI, SPCCI Ignition!