if it is just 2 of you then putting water jugs on the rear seat floor is even better. Pack the rear seat with heavy items helps. More weight in the truck give more control.
My brother bought a 24 foot box camper with the mercedis 3.0 liter turbo diesel engine and tows his chevy spark . he get 14 MPG at 65 MPH level interstate
Attach it to a custom made tonnel cover and you can store heavy stuff in the bed in front of the rear wells to keep some weight out of the trailer. the stationary piece of the tonnel cover would probably be the center piece.
I am averaging 45.7 (MPG gage) from day 1 on my hybrid for 2 years June 10-2024 to June 11-2026. I live in zone 6 USDA Cincinnati, Ohio. My MPG read about 5% higher than calculated. I run 42 PSI front tires 35 PSI rear tires. Front end is heavier.
after a long drive to Chattanooga TN from Cincinnati averaging 65-70MPH with time lost on drive thru food stops
the actual MPGs will be between 46-47 calculated temperatures bounced betwee 80F-87F
Just tanked up at 591.7 mile will 11.35 gallons after my standard 2 click to get 52.12334801762115 MPGs. My MPG gage read 55.6 MPGs Lots of Bondo for the bullet holes.