What can cause engine knock or pinging?

Engine knock or pinging is primarily caused by the fuel-air mixture igniting prematurely within the combustion chamber. This premature ignition can be influenced significantly by the fuel's octane rating. If the fuel being used does not have the appropriate octane rating for the engine's design, it can lead to knocking.

Higher octane fuels are designed to withstand the pressures and temperatures found in the combustion chamber without igniting too early. When a lower octane fuel is used, it may combust before the piston reaches the top dead center, resulting in knocking or pinging sounds as the combustion occurs out of sync with the engine's cycle.

In contrast, high-quality fuel often implies that it meets the required octane ratings suitable for the engine, thereby reducing the possibility of knocking. Over-lubrication and low tire pressure do not directly impact the combustion process in a way that causes knocking, as they primarily relate to engine mechanics and vehicle handling, not the fuel's combustion characteristics.