Emissions have brought down diesel efficency. They lowered compression and fuel air enrichemnt. they raised engine size to compensate somewhat. Hp and Torque Figures well... The Pig --- injection with cat does lower emissions but at a price. Fords with accumulated miles are facing problems with corrosion.The others may too. The Cummins, in Dodge still gets away without the DEF doesn't it? The recirculation and after burn presents it's own problems.
You burn more fuel so you get more emissions, in the same mileage, maybe not in this case but you sure spend a lot more money, for the engine/emissions hardware, RV and fuel.
When they took the sulfur out, of diesel it caused lubricity problems, which they denied and advised you shouldn't /didn't need to run lubricity agents or any additives. Then the biodiesel besides serving Big Ag was to counter the lubricity problem and so on.
There only concern is emissions not our pocketbook and they still miss the mark.
Ethanol is the biggest boon doggle and most expensive for Americans except....