You won't find a single definitive answer. However, you can expect somewhere in the range of 10-15 MPG (miles per gallon) as a *very rough estimate*. It's likely to be on the lower end of that range for heavier use or larger engines. For city driving, it would likely be even lower.
To get a more accurate idea, you would need to specify the exact engine size and options of the particular truck. Checking the original owner's manual (if available) would provide the most reliable fuel economy figures.
