Gary Lewis wrote
A 460/C6 combo does poorly with no load, so I can only assume that with a load like that it would be really poor.
Our '72 F250 w/a 4V 390/C6 carrying our 9 1/2' camper got as low as 7 MPG in adverse conditions - like a head wind.
I'm pretty sure our 1993 E350 RV only got 8mpg...maybe 8.5, but that was an EFI 460 with an E4OD. It was also 31 feet long with dual wheels, so it was certainly wasn't light. It had great power though!
We were lucky enough to have owned it during the lowest point of the Covid lockdowns when gas was only 70 cents a liter here, and even then it cost $150-ish to fill. It would be $450-$500 now. Eeek.
1994 F150 4x2 Flareside. 5.0 w/MAF, 4R70W, stock.
1984 F150 4X2 Flareside. Mild 302 w/ 5spd. Sold.
1980 F150 4X4 Flareside. 300i6 w/ 5spd. Sold in 2021.
1980 F100 4X2 Flareside. 351w/2bbl w/NP435. Sold in 1995