How does an engine use compression?

An engine utilizes compression primarily to increase the temperature and pressure of the air-fuel mixture before combustion occurs. This process is essential for the efficient operation of internal combustion engines. When the engine piston moves upward in the cylinder during the compression stroke, it compresses the air-fuel mixture, significantly raising its temperature and pressure.

This elevated temperature and pressure are critical for ensuring that the mixture ignites efficiently when it comes into contact with the spark from the spark plug (in gasoline engines) or through compression alone (in diesel engines). The high-pressure environment enhances the combustion process, leading to more power generation and improved engine performance.

The other options do not accurately represent the primary function of compression in an engine. For instance, while compression can have an indirect effect on fuel consumption, it does not directly aim to decrease it, and it certainly doesn't serve as a means to cool the engine or reduce noise.