Bought an old C one time where the gauge didn't work. First trip was about 1500 mi one way. Threw a 5 gal can of gas in the trailer and took off.
Previous owner told me it had a 45 gal tank. Figured 6mpg x 40= 240mi. About 230mi later I was on the side of the Ohio Turpike. Threw in the 5gal and hit a station 2mi down the road. It took 30gals to fill it. Seems the PO missed it by 10 gals.
After that, it was fill up every 200mi and always carried a can. Put another 15,000 on the ol' girl and never another problem. Luckily, the odometer kept working