To "reset" fuel-related information, you'll need to:
* Reset the trip odometer: This is usually done by pressing and holding a button on the instrument cluster (often near the speedometer). Consult your owner's manual for the precise location and procedure. This will reset the miles driven since the last reset, allowing you to track fuel consumption for a specific period.
* Clear average fuel economy: Some 1998 F-150s might have a way to reset the average fuel economy calculation, but it's not universally standardized across all trims. Again, check your owner's manual for instructions specific to your truck. If it doesn't have this feature, the average will simply recalculate over time as you drive.
In short, there's no single "fuel reset" button. You reset relevant fuel data by using the trip odometer reset function in your instrument cluster. The owner's manual is your best resource for exact instructions.