Octane booster, will it damage the engine or be a waste of money?

The only time you need octane booster is when you are demanding more power form the engine, for everyday driving you don't need it.

Using a higher octane fuel than your vehicle's recommended octane rating typically doesn't lead to improved fuel mileage or performance. Octane rating refers to the fuel's resistance to pre-ignition or knocking, which is most relevant in high-compression engines. Using a higher octane fuel than necessary in an engine designed for regular 87 octane might not yield any noticeable benefits and could be a waste of money.

In your case, if your vehicle's manufacturer recommends using 87 octane fuel for the 5.3L Z motor, switching to 91 octane might not provide any significant advantage in terms of fuel mileage or performance. The engine's design and calibration are optimized for a certain octane level, and using higher octane fuel won't necessarily result in better efficiency.

Using octane booster additives in a vehicle designed for lower octane fuel could be a waste of money and might not provide any noticeable benefits either. Modern engines and fuel systems are designed to work efficiently with the fuel octane level they are calibrated for.

In terms of potential damage, using a higher octane fuel or octane booster additive is unlikely to cause immediate harm to your engine, but it's not necessary and could be an unnecessary expense. However, if your vehicle has a history of knocking or pre-ignition issues and using a higher octane fuel helps mitigate those problems, you might consider discussing this with a professional mechanic.

If you're interested in improving fuel efficiency, there are more effective ways to do so:

Regular Maintenance: Keeping your vehicle well-maintained with proper oil changes, air filter replacements, and tire maintenance can significantly impact fuel efficiency.

Driving Habits: Efficient driving practices, such as smooth acceleration and braking, maintaining a consistent speed, and avoiding aggressive driving, can help improve fuel mileage.

Proper Tire Inflation: Keeping your tires properly inflated can reduce rolling resistance and improve fuel efficiency.

Minimize Weight: Removing unnecessary items from your vehicle and avoiding carrying excessive weight can improve fuel efficiency.