It's important to use the octane rating recommended by the manufacturer to ensure optimal engine performance and fuel economy. Using a lower-octane fuel than recommended can lead to knocking or pinging, which can damage the engine. Using a higher-octane fuel than recommended does not provide any additional benefits and can be a waste of money.
If you're not sure which octane rating to use for your Hyundai, you can always check the owner's manual or consult with your local Hyundai dealership.