Thinking of trucks, the easiest way to increase a trucks FE is to decrease its frontal area AKA skinny, best examples are kei trucks, there is one Daihatsu in CA legally licensed has a turbo 660cc 2 cycle with a dual range 6sp transmission and 4wd. He bought it from the parks service, small as it is rated at 3/4 ton and he pulls an 20ft enclosed trailer with it. And it is dimensionally very small, without a load it gets in the 30's for FE
Perhaps time to reconsider how trucks are rated and built, there are many who use a truck but need a full size because of weight and strength limitations & reliability not because they need the full dimensions of the bed.
Just a thought, I love kei trucks but wish they were longer with a diesel
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