I don't know how to explain the CRV's performance but it's reality.
We typically get 28 mpg highway driving at 65 mph when not towing.
We typically get 23 mpg highway driving at 55-57 mph when towing.
Here are the details of our rig and approach to trailering:
In both cases we are mostly in our highest gear, 5th. We do have a manual transmission and I always keep the RPM above 2000, usually between 2000 and 3000 rpm.
We typically do not run the tow vehicle air conditioner, primarily because we do little warm weather traveling. When we travel in the summer we are usually heading north.
I also boost the pressure of the Honda's tires
well above normal (24-26) with the rears at 39 and the fronts at 32. I suspect that helps a little. I believe stiffening the rear tires
helps support the tongue and potential side forces.
We are not rapid accelerators. On our trip home from Florida this spring we only passed two vehicles.
The Honda now has 140,000 miles on it. The only service we perform are fluid changes, filter changes and brake pad replacements. Actually it has the original plugs, they probably should be replaced.
We are also great waxers, keeping both the tow vehicle and trailer waxed.
We also have no roof protrusions, like Max vents or roof air conditioners, reducing the frontal area a little. As well we do not have an awning
on the Scamp
Our RVs are usually among the lightest in their class after packing. We do not carry stuff unless we plan to use it. (This is a change from our Motorhome days where the underneath storage is greater than the volume of a Scamp
. We're presently emptying the Bounder getting it ready to sell. When we started RVing in the Bounder we thought we had really down sized. The Scamp is another level of downsizing, even from our former Sunline.)
Even though we're gone for months at a time, we keep it light
I know nothing about your cargo trailer but I will say the Scamp and Casita
were 15% better than the boxy Sunline (20 mpg) we used to tow. The bottom line is shape, frontal area and speed.
I hope this all helps.