The MPG on a 1992 Ford F-150 Custom varied significantly depending on the engine, transmission, and driving conditions. There wasn't a single MPG figure. You could expect figures ranging from
10-17 MPG in city driving and 14-20 MPG on the highway. The larger the engine, the lower the MPG.
To get a more precise estimate, you'd need to know the specific engine size (e.g., 4.9L, 5.0L, 5.8L, 7.5L) and transmission type (manual or automatic).