U Haul truck beat up and horrible gas mileage Phoenix, Arizona

Picked up latest Uhaul 26' with car hauler for another 1500 mile move. The truck was beat up so bad the guy said when I get to the drop off if there were any questions to have them call him but since I had the Safemove insurance there shouldn't be a problem. He said when he picked it up the night before it ran "OK" like something was wrong. My husband asked what he meant by ok and he said oh no, it ran alright. First night on the road we seriously thought the thing was going to break down. It back fired constantly and never would shift into overdrive. It did this the entire trip as well as there was apparently exhaust coming into the cab, the air barely worked, and the front end shook when over 40 mph. We had our 9 month old with us and I was not happy. The worst though was the gas mileage. We spent $1200 to go 1500 miles. One fill up on a 57 gallon tank took us 171 miles on the flats of Oklahoma. We did the same trip 6 months prior but also was driving another vehicle behind and was loaded far heavier. The gas prices were higher at that time yet we still spent $400 less on fuel. I have a complaint in but no one calls me back. I have used Uhaul for years but after this I never will again.