What is the likely consequence of using a fuel grade that is lower than specified for the engine?

Using a fuel grade that is lower than specified for the engine can lead to detonation. Detonation occurs when the fuel-air mixture in the engine's cylinders ignites earlier than intended, which can create a shock wave that damages the engine components. This phenomenon is particularly concerning in high-performance engines that rely on specific octane ratings to function efficiently and safely.

Lower octane fuel does not resist knock or detonation as effectively as higher-grade fuels, which are designed to handle the compression ratios found in more powerful engines. When the engine experiences detonation, it can lead to serious issues such as engine roughness, loss of power, and, in severe cases, catastrophic engine failure due to structural damage.

The other options do not accurately represent the effects of using a lower-grade fuel. Increased engine efficiency, reduced fuel consumption, and lower operating temperature are not outcomes associated with using a fuel that does not meet the recommended specifications. In fact, they may hinder performance and lead to further issues down the line.