Kinda hard to believe that higher speed, more drag, more rolling resistance, etc resulted in less fuel usage. Generally higher speed means higher HP output which means more fuel. Must be a transmission gearing thing...maybe overdrive is too over...and engine is lugging in an inefficient RPM range.
-Eric E. 2006 Fleetwood Discovery 39S, Cat C7, Allison 6 speed, Freightliner. CFII/MEI Beechcraft Specialty. Gulfstream Contract Pilot.