Ford F-650 2001 Owner's Manual page 190

Maintenance and care
The amount of Empty Reserve varies and should not be relied
upon to increase driving range. When refueling your vehicle after
the fuel gauge indicates empty, you might not be able to refuel
the full amount of the advertised capacity of the fuel tank due to
the empty reserve still present in the tank.
Filling the tank
For consistent results:
• Use the same fill rate setting (low — medium — high) each time
during filling.
• Allow three automatic click-offs when filling.
• Always use fuel of a known quality, preferably a national brand.
• Have the vehicle loading and distribution the same every time.
• When refueling a vehicle equipped with dual fuel tanks, if the two
tanks are not filled equally, the fuel gauge reading may fluctuate
slightly until the fuel level between the two tanks balance out and
become equal.
Your results will be most accurate if your filling method is consistent.
Calculating fuel economy
1. Fill the fuel tank(s) completely and record the initial odometer reading
(in kilometers or miles).
2. Each time you fill the tank(s), record the amount of fuel added (in
liters or gallons).
3. After at least three to five tank fill-ups, fill the fuel tank(s) and record
the current odometer reading.
4. Subtract your initial odometer reading from the current odometer reading.
5. Follow one of the simple calculations in order to determine fuel economy:
Multiply liters used by 100, then divide by total kilometers traveled.
Divide total miles traveled by total gallons used.
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