Diesels are inherently higher in torque but also much more efficient than the gas counterparts. The air/fuel ratio advantages are explained here.
https://rentar.com/diesel-engines-fu...oline-engines/
The 2018 Freightliner I drive is so much more advanced from engines just a few years ago. It gets 8.5 to 10 mpg moving up to 80K pounds with 2:73 gears with the engine turning 1220 rpm at 65 mph. 15 or 20 years ago the norm was 5-6 mpg for semi trucks.