What is an effect of using low-quality fuel in an engine?

Using low-quality fuel in an engine can lead to increased emissions and engine knocking, which are significant concerns for engine performance and environmental impact. Low-quality fuels often have impurities and a lower octane rating, which can cause improper combustion within the engine cylinders. This improper combustion is what leads to engine knocking, a condition where the air-fuel mixture detonates prematurely, creating a knocking or pinging sound. This not only reduces the efficiency of the engine but can also cause damage over time.

Additionally, low-quality fuels can result in incomplete combustion, leading to higher emissions of harmful pollutants like carbon monoxide and hydrocarbons. These emissions contribute to environmental pollution and can also indicate that the engine is not operating optimally, potentially leading to more frequent repairs or maintenance issues down the line.

The other options reflect potential benefits or neutral effects that are unlikely with low-quality fuel. High-quality fuel is essential for optimal engine performance, efficiency, and longevity.