Hypomiling
 

I had to drive a 24-foot UHaul truck to Houston and back from Louisiana. It got 7 mpg. :/ Made me appreciate the Yaris. I had to keep putting gas in it over and over...

Speed?

75 mph haha it had a governor

Oddly enough, its engine is only 4 cylinders

Wow, that's pretty horrible :p Was it fully loaded on both runs?

4 cyl turbo diesel? Like a cummins or isuzu?

4 cylinder gasoline lol....not loaded fully

You were probably running the engine too hard and making it run rich. On such a big truck, you could probably just hold it at its peak efficiency point since aerodynamics would limit speed.

Likely geared low
 

Maybe 15 years ago I was helping a friend move. I turned out he got "bait and switched" by the local U-haul and brought back a truck with a manual transmission. He doesn't drive stick and wasn't going into details on his 3 mile jaunt down route 1.

From what I remember (this is probably the empty truck on the way back): 1st gear - moves the tires, once the tire begins rotating switch to second (as in a couple of feet). You should be in third gear by the time you leave the intersection.

This doesn't leave much room for high gears, much less any overdrive. It does allow you to load up a lot of weight on a 4 cylinder engine and still get it moving (slowly). I suspect that the truck in this thread is geared a bit taller than the one I drove, I think they would have to put a limiter below 75 on mine (note that I survived the DC beltway, so I wasn't going all that slow).

PS. I have no idea if you can still get manual transmission U-hauls.