Generally, diesel engines are more fuel-efficient than gasoline engines, particularly for larger vehicles such as trucks and buses. This is because diesel engines operate at higher compression ratios and utilize the compression ignition process, which results in better fuel conversion efficiency. Additionally, diesel engines often have turbochargers and intercoolers that improve engine efficiency by increasing air density and reducing fuel consumption.
On average, diesel engines can achieve fuel efficiency in the range of 25 to 35 mpg (10.6 to 14.7 km/l) for passenger vehicles and 5 to 10 mpg (2.1 to 4.3 km/l) for heavy-duty vehicles. However, these values can vary significantly depending on the specific vehicle and operating conditions.
It's worth noting that while diesel engines are known for their fuel efficiency, they also produce higher levels of particulate matter (PM) and nitrogen oxides (NOx) emissions compared to gasoline engines. These emissions can have negative impacts on air quality and public health, particularly in urban areas. To mitigate these environmental concerns, modern diesel engines are equipped with emission control systems such as diesel particulate filters (DPFs) and selective catalytic reduction (SCR) systems to reduce harmful emissions.
Overall, the diesel consumption of an engine depends on various factors, but diesel engines generally offer better fuel efficiency compared to gasoline engines, especially for larger vehicles and applications requiring high torque.
