What is the purpose of using octane boosters in SI engines?

The purpose of using octane boosters in spark ignition (SI) engines is primarily to enhance the octane rating of the fuel. Higher octane ratings allow the engine to operate more efficiently under higher compression ratios and can help prevent engine knocking or pinging, which occurs when the fuel-air mixture detonates prematurely. By improving the fuel's octane rating, octane boosters allow for a more controlled and stable combustion process, ultimately leading to better engine performance.

While increasing fuel economy, improving ignition timing, and reducing emissions can be secondary benefits in some cases, the main function of octane boosters is to raise the octane level of the fuel. This allows the engine to perform optimally and can lead to enhanced power output and efficiency, especially in high-performance or modified engines designed to run on higher octane fuel.