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.
Can using premium gas actually save me money in the long run?
For the vast majority of vehicles, using premium gas does not save money. The primary reason is that premium fuel costs more per gallon, so you are immediately spending more on each fill-up. The only scenario where premium fuel might indirectly lead to savings is if your car is specifically designed to require premium fuel for optimal performance and efficiency. In such cases, using the recommended premium fuel can prevent engine knocking, maintain engine health, and achieve the manufacturer's stated fuel economy figures. If your car runs perfectly on regular gas, switching to premium will only increase your fuel expenses.