Fuel mileage still sucks

[Redland1]

I have an 03’ International 9900i with 3.90 gear ratio and 13 speed.I purchased the truck to haul Frac sand here in south Texas and started out with a grain hopper hauling 84k with the overweight permit and then the company I was with went to boxes for a lil bit and then back to hopper bottoms.I averaged 5.8 mpg driving at 65mph,taking off nice and easy,and didn’t idle a lot even with all the staging pad time.My truck is a wall going down the road compared to your aero truck.