What is a typical consequence of engine knock in performance?

Engine knock, also known as detonation, occurs when the air-fuel mixture in an engine's cylinder ignites prematurely, resulting in a knocking or pinging sound. This phenomenon typically leads to inefficient combustion, causing an increase in combustion pressure and temperature. One of the most significant consequences of engine knock is the potential for engine damage.

When knock occurs, the force generated can create excessive stress on engine components, such as pistons, cylinder heads, and connecting rods, leading to problems like scoring, cracking, or even complete system failure if not addressed. Over time, persistent knocking can degrade the engine's performance, lead to costly repairs, and ultimately shorten the engine’s lifespan.

In contrast, the other options suggest improvements or benefits to engine performance or efficiency, which do not align with the detrimental effects of engine knock.