Rather than guesses from armchair quarterbacks, may I provide a real world example.
We just completed a 3363 mile trip towing our
Trillium 4500 from Nova Scotia to PEI, New Brunswick, Quebec, Ontario and back to Nova Scotia taking in the Maritime Vintage trailer show along the way. We were two adults, a child, a dog and all our gear. We weighed our loaded trailer with half a tank of water at a roadside weigh scale at 2050 lbs. We averaged 19-20 mpg on flat ground and 16-17 mpg on hilly ground while keeping the speed to 60-65 mph.
Our 4 cylinder Rav4 performed flawlessly 😊