Fuel Selection Matters: Higher RON Does Not Guarantee Optimal Vehicle Performance

JAKARTA — Vehicle owners often pay attention to using fuel with a RON (Research Octane Number) rating lower than the manufacturer’s recommendation, as it can cause engine problems. However, many drivers also choose petrol with an octane number higher than the recommended specification.

“Combustion is heavily dependent on the match between fuel RON and the ignition timing or spark advance settings on the engine. If they don’t align, the result is actually suboptimal,” explained Tri to Kompas.com on Thursday, 5 March 2026.

Tri clarified that using fuel with a RON rating higher than the manufacturer’s recommendation does not automatically increase vehicle performance or improve fuel economy. This is because the engine’s ignition system is calibrated based on the characteristics of a specific fuel type.

When the octane rating is too high, the combustion process may occur at a non-ideal time within the combustion chamber. As a result, the power generated by the engine may decrease. When power output drops, drivers typically press the accelerator more forcefully to achieve their desired performance.

Additionally, suboptimal combustion can also increase exhaust emissions. Tri noted that similar conditions can occur in motorcycles, which generally have simpler engine configurations compared to modern cars.

“If a motorcycle’s engine is set for a certain RON, say RON 90, and you fill it with higher RON fuel, the acceleration can feel heavier,” said Tri.

For this reason, Tri advised vehicle owners to follow the fuel recommendations provided by the manufacturer. Beyond maintaining efficiency, using petrol according to specification helps the engine operate more optimally.