A back-of-the-envelope calculation tells me that the efficiency of a powered airship is about the same as modern airplanes. Switching truck freight to airships would use an order of magnitude more fuel.
Higher, as long as the airship for not have to go fast and can use air currents mostly like any old balloon. It can go almost arbitrarily slow, as long as the weather is good and there is no time pressure.
The main efficiency losses in airplanes are wind resistance and takeoff/landing... An airplane cannot go arbitrarily slow or it loses lift.
According to industry sources, airships are about 80% more efficient.
Plus as fuel space efficiency and weight is less of a problem, they can use different fuel sources for the engines, including methane or hydrogen, and electric engines too.
