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yeah. I think He may be confusing fuel economy in big diesel trucks and smaller gasoline versions. The fuel has more energy density and the compression makes it efficient to run them at certain speeds. The torque thing is true. A lot of new engines are actually either direct inject. Or they have variable cylinder firing. The Chrysler Hemi™ can shut down and run on 4 cylinders for light load highway driving. With regards to torque. I would say that a certain diesel truck would generally require less fuel for driving on a flat surface than a gasoline version. You can think of the higher compression, longer stroke, to generally move the parts a further distance for the same amount of gas. This translates, in turbo diesel GM type motors with around 450HP, will have a condition that opens the waste gate the boost goes down and as a result the injectors put in less fuel, you get a charge that can be timed to go off at a certain time and you get a smaller more direct flame which will still send the engine around 1 time for each of the 4 cycles.
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