Regular vs premium petrol: Is the pricey fuel in India really worth it for your car?

After the Bharat Stage VI emissions norms were implemented in 2020, petrol’s minimum octane rating was upped from an average baseline of 88 RON to 91 RON (Research Octane Number). As of now, regular E20 petrol is claimed to carry a much higher baseline of around 95-98 RON, while premium fuel, such as XP95 or Power95, offers a similar octane rating alongside additives to clean the fuel system. Consumers can also choose high-octane petrol rated for 100 RON with little to no ethanol content. While this seems like the way to go if you want to avoid ethanol content in your fuel, 100-octane petrol costs about ₹60 per litre more than regular petrol, bringing diminishing returns for cars which do not require it.

So, what should you give your car? Premium or high-octane petrol is considered the go-to for engines with high compression ratios, found in performance-focused sports cars. This is more refined, and cars which use it are likely to produce fewer emissions. Yet, feeding high-octane fuel to an engine that does not require it will not bring you more performance or mileage, and in some cases may be detrimental to your fuel economy. At the same time, premium petrol below 100 RON still contains 20 per cent ethanol. E20 petrol is corrosive, and while most modern cars built after 2020 are designed to run on it, owners will have to accept the inevitable drop in mileage.

What do the numbers mean?

The level of octane and ethanol is adjusted at the time of blending different streams of fuel to create the desired petrol blend. The RON reflects the amount of compression that a specific blend can handle before combusting by itself. Petrol high in octane does not pre-ignite quite as easily as regular petrol and is suitable for high-performance engines that demand a higher heat-bearing capacity.

(Also read: E20 petrol – Good, bad and better)

But does it really make a difference?

At the moment, regular petrol and premium petrol below 100 RON carry minimal differences. Both regular E20 and premium petrol carry approximately the same petrol-ethanol ratio. Furthermore, recent lab studies have shown that regular petrol now offers between 95-98 RON, often matching or exceeding the octane rating offered by premium petrols such as Power95 or XP95. Here, the only difference lies in the additional cleaning properties of premium petrol.

Ethanol heavily attracts moisture and can lead to water accumulation in the fuel over time. If stored for longer, ethanol and water start to form a separate layer at the bottom of the tank, depleting octane levels in petrol. This is why slow-selling 100 RON petrol is effectively ethanol-free, carrying between 0-0.2 per cent of ethanol content. This type of petrol sells in far fewer numbers and typically sits in underground tanks for longer durations. As such, manufacturers would rather avoid the logistics and storage costs of maintaining small batches of XP100 blended with ethanol.

Who needs premium petrol?

Manufacturers generally state the type of fuel the car needs and if it is recommended to use a certain petrol blend. The types of petrol available currently in the market are all high in octane, with both regular E20 and premium petrol, such as Power95, XP95, etc., both offering in the same ballpark of 95-98 RON. Additionally, almost all grades below 100-octane fuel offer similar ethanol content. 100 RON petrol continues to be ethanol-free, providing a purer, but pricey alternative that does not wear out your engine components.

If you own a regular car, you are more than safe to choose the standard E20 option, but you can choose to pay the extra if you think your car can benefit from the additives. However, the trade-off is small, and buyers can choose to stick to E20. Even if it carries a cause for concern, most modern vehicles built after 2020 can cope with it for several years. However, ethanol-blended fuel carries a much lower energy density, resulting in less performance per litre alongside the mileage drop.

100 RON fuel is ethanol-free and has a much higher heat bearing capacity. This is good for vintage cars or high-performance cars: Classic cars have much older fuel systems which are highly vulnerable to E20, and owners of such vehicles can use non-corrosive petrol such as XP100 to maintain their possession. Additionally, high-performance cars demand a high heat-bearing capacity to extract more power, and 100 RON petrol will give you more energy per litre.