The gas mileage on a 1978 Ford F-350 460 Camper Special will be
very poor by modern standards. Expect to get somewhere in the range of
6-8 miles per gallon (mpg), and possibly even less depending on driving conditions, load, and the condition of the engine and carburetor. Factors like terrain (hills significantly reduce fuel economy), speed, and even tire pressure will all heavily impact the fuel efficiency.
It's important to remember that these are just estimates. Actual mileage will vary considerably.
