The diesel engine itself as a concept yes, but the issue is on modern diesel trucks (talking pickup trucks) all the expensive stuff starts going out after 150k miles, so sadly that isn't the case anymore for the average truck buyer. Higher mileage can be achieved in the trucks always working, but the ones that are driven to the grocery store and back empty will have emissions system issues.They're also beneficial if you keep a vehicle a long time. I have 220,000 on one of my diesels, but it's all in town driving, so it has like 11,000hrs on the engine if I remember right. I think about 5,000hrs is all you get from a gas engine.