Octane rating describes petrol’s resistance to knock in standardised tests. It does not measure energy content, cleanliness or a guaranteed power gain. Its practical value depends on the engine’s compression, boost, temperature and ignition strategy.
Why knock resistance matters
Under high pressure and temperature, part of the mixture can auto-ignite before normal combustion is complete. Higher-octane fuel gives more resistance to this behaviour and can provide useful margin in a demanding petrol engine.
How the ECU reacts
Modern engines monitor knock and may reduce ignition advance when necessary. Some adaptive calibrations can take advantage of better fuel; others simply use the additional safety margin. A higher number at the pump does not force the engine to make more power.
Fuel must match the calibration
If a Swaptune calibration is prepared for a stated minimum octane, the driver must use fuel meeting that requirement. Mixing fuels or changing grade changes the available margin, especially under sustained load.
FAQ
Is 98 RON more energetic than 95 RON?
Not because of its octane number. Octane measures knock resistance.
Can octane booster replace correct fuel?
Do not assume so. Product composition and final concentration vary.
Does diesel have an octane rating?
Diesel ignition quality is described using cetane, a different property.