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.
When should I choose regular gas over premium gas?
You should choose regular gas (87 octane) if your vehicle's owner's manual specifies it as the recommended or required fuel grade. Most cars on the road are designed to run efficiently and reliably on regular gasoline. Using regular gas in a car that doesn't require premium is the most economical choice and will not negatively impact performance or engine health. Premium fuel is only beneficial for vehicles specifically engineered to take advantage of its higher octane rating, such as those with high-compression engines, turbochargers, or superchargers, where it prevents engine knock.