Can XL Service Bodies improve fuel economy?

Yes! Fuel prices are a major expense regardless of which vehicle you drive, however the XL Service Body fitted to a normal cab chassis can help you save fuel by presenting a minimal frontal area – imagine running down the road with a 2400 x 1200 piece of ply like a sail! It would be quite difficult especially if the ply doubled in size or you tried running faster.  A large frontal area increases drag which severely affects fuel economy. Ladder racks and ladders can also affect the drag coefficient, so be aware of this especially when travelling large distances.