Why better mileage on diesel than gas?

Diesel engines are generally more fuel-efficient than gasoline engines due to their higher energy density and thermodynamic efficiency. Diesel fuel contains more energy per gallon than gasoline, allowing vehicles to travel further on the same amount of fuel. Additionally, diesel engines operate at higher compression ratiOS, which leads to better combustion efficiency and lower fuel consumption. As a result, diesel vehicles often achieve better mileage compared to their gasoline counterparts.