Forget about MPG's and drive with traffic staying in safe road position. The dynamics of road vertical ups and downs, negates the sweet spot due to the weight push going down and the weight drag going up grades. Sweet spots are even useless in flat terrain as traffic dictates the safest speed. Proper tire inflation to the load is more important than sweet spot RPM's. Just know enough to speed up and slow down at RV smooth and safe rates. 8 seconds behind any vehicle in front of you at 60 MPH and merge into moving traffic with signals and accelerate to traffic speed ASAP, even if it means putting the pedal to the metal. SAFETY IS MORE IMPORTANT THAN SAVING A FEW PENNIES.
