Fuel consumption drop of no more than about 40% given same road at same speed when tow vehicle is solo.
Run a 200-mile loop back to the same filling station on the Interstate. Use cruise control.
Anything much above 40% is worth investigation. Trailer axle alignment is nearly never correct. TT tire pressure should be to sidewall max. Bearings and brakes should be serviced even if brand new. All vehicle service should be to book standard less 15% deductions for time/mileage.
WDH adjustment should be a minimum of 100% FALR. TV brake drag and alignment should be checked. TV tire pressure should be according to load once WD is proper and each wheel position is weighed to find heaviest tire load on each axle (then to TV manufacturer guidelines; "more" is not better).
Fuel and campground costs are he honest daily expenses while en route. Worth your time to find the range of WD adjustments on a scale that your rig will see with varying loads. And to tighten up the rest.