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 are the actual benefits of using premium gasoline?
Premium gasoline, typically 91 or 93 octane, offers benefits primarily for vehicles with high-compression engines or turbocharged/supercharged engines designed to take advantage of its higher resistance to knocking. These engines can operate at higher pressures and temperatures, allowing for more aggressive ignition timing and potentially leading to increased horsepower and improved fuel efficiency. For the vast majority of vehicles designed for regular 87 octane fuel, premium gasoline provides no performance advantage and simply costs more. The key benefit is preventing knock in engines specifically engineered for it.