Which type of engine typically utilizes a higher compression ratio for better efficiency?

Diesel engines are known for utilizing a higher compression ratio compared to other engine types, which significantly contributes to their efficiency. The fundamental principle behind diesel engines is that they operate by compressing air to a high degree before fuel is injected. This compression raises the air temperature to a point where the fuel ignites spontaneously, facilitating a more complete combustion process.

The higher compression ratio allows diesel engines to extract more energy from the fuel, improving thermal efficiency and providing greater torque at lower engine speeds. This is one of the reasons why diesel engines are widely used in applications that require sustained power and efficiency, such as in heavy-duty vehicles and machinery.

In contrast, gasoline engines generally operate at lower compression ratios primarily due to the fuel's propensity to knock when subjected to high compression levels. Rotary engines function uniquely and do not conform to the same compression principles as cylinder-based engines. Two-stroke engines are designed for power efficiency in a different manner, taking advantage of different cycles of operation, but they do not achieve the same compression ratios as diesel engines. Thus, the characteristics of diesel engines in terms of compression ratio directly correspond to their high efficiency.