Is High-RON Petrol More Fuel-Efficient? An Explanation Based on Engine Compatibility
Many vehicle owners assume that using petrol with a higher octane rating, or Research Octane Number (RON), will make fuel consumption more efficient. This assumption is not entirely wrong, but it does not apply to all types of vehicles. In reality, the level of fuel efficiency is not solely determined by a higher RON, but by the compatibility between the fuel type and the vehicle’s engine specifications. If the fuel used matches the engine’s compression ratio, the combustion process will be more optimal, allowing fuel consumption to become more efficient.
RON is a measure that indicates a fuel’s ability to withstand high pressure and temperature in the combustion chamber before igniting from the spark plug. The higher the RON, the greater the fuel’s resistance to compression pressure. This results in more stable combustion and reduces the risk of detonation or knocking, especially in engines with a high compression ratio. In Indonesia, petrol is available in several RON options, ranging from RON 89 and RON 90 such as Pertalite, to RON 92 like Pertamax, and up to RON 95, RON 98, and RON 100. Each is designed to meet the needs of engines with different characteristics.
Petrol with a higher octane rating can indeed make fuel consumption more economical. However, this is only true if the fuel type used matches the vehicle’s engine compression ratio. In engines specifically designed to use high RON, such as RON 92 or RON 95, combustion will be more complete and stable. This condition produces more optimal power, so the engine does not have to work as hard to deliver the same performance. This combustion efficiency can ultimately help reduce fuel consumption, making the vehicle feel more economical compared to using fuel with a lower octane rating than the manufacturer’s recommendation.
Every vehicle engine is designed with a different compression ratio. The compression ratio is the comparison of the combustion chamber volume before and after the piston completes its compression stroke. The higher the engine’s compression ratio, the greater the pressure the fuel receives in the combustion chamber. Therefore, high-compression engines require high-octane fuel to prevent premature combustion or knocking. Conversely, low-compression engines do not require high-octane fuel. The key is not using the highest RON, but using the RON that matches the vehicle’s specifications. Information regarding the recommended RON can usually be found in the vehicle’s owner’s manual or official manufacturer guidelines.
As a general guide, RON selection can be adjusted to the engine’s compression ratio: engines with a compression ratio of 9:1 to 10:1 are generally suitable for RON 90; a ratio of 10:1 to 11:1 typically recommends RON 92; and a ratio above 11:1 is more suited to RON 95 or higher. However, this guidance is general. Each vehicle manufacturer may have different engine specifications, so the official manufacturer’s recommendation remains the primary reference for choosing fuel.
Beyond the RON, fuel consumption is also influenced by various other factors, including engine condition and maintenance, tyre pressure, vehicle load, driving style, traffic conditions, use of air conditioning, and fuel quality. This means that using high-octane petrol alone is not enough to make a vehicle more fuel-efficient if these other factors are neglected.