Using 91-octane premium fuel instead of 87-octane regular fuel will only increase your engine's power if your car's manufacturer specifically designed the engine to require it.
Higher octane fuel resists knocking or 'pinging' under compression, which is a premature ignition of the fuel-air mixture. Engines designed for higher octane can take advantage of this resistance to operate at higher compression ratios or with more advanced timing, which can lead to increased horsepower and efficiency. However, if your vehicle's owner's manual specifies regular 87-octane fuel, using premium 91-octane will likely offer no discernible performance benefit and is generally not recommended. Always consult your vehicle's manual for the correct fuel grade.
Fuel octane requirements are determined by the vehicle manufacturer and using a higher octane than recommended typically provides no benefit.
What does octane rating mean for my car's performance?
The octane rating indicates a fuel's resistance to engine knock, which is an uncontrolled explosion of the fuel-air mixture within the cylinder. Higher octane fuels are less likely to knock under pressure. If your car's engine is designed with a high compression ratio or advanced ignition timing, it may require higher octane fuel (like 91 or 93) to prevent knocking. Using the recommended octane allows the engine to perform as designed, potentially offering optimal power and efficiency. Using a lower octane than recommended can cause knocking, reducing performance and potentially damaging the engine.