Ford 2013 F-650 Owner's Manual page 120

Note: The amount of usable fuel in the 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.
For consistent results when filling the fuel tank:
• Turn the ignition off before fueling. An inaccurate reading results if
the engine is left running.
• Use the same fill rate (low–medium–high) each time the tank is filled.
• Allow no more than two automatic click–offs when filling.
• 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 balances out and
becomes equal.
Note: For vehicles equipped with dual fuel tanks, engine performance
may degrade if fuel is not added to both tanks when refueling.
Results are most accurate when the filling method is consistent.
Calculating Fuel Economy
Do not measure fuel economy during the first 1000 miles
(1600 kilometers) of driving (this is your engine's break-in period); a
more accurate measurement is obtained after 2000–3000 miles
(3200–4800 kilometers). Also, fuel expense, frequency of fill-ups or fuel
gauge readings are not accurate ways to measure fuel economy.
1. Fill the fuel tank completely and record the initial odometer reading.
2. Each time you fill the tank, record the amount of fuel added.
3. After at least three to five tank fill-ups, fill the fuel tank and record
the current odometer reading.
4. Subtract your initial odometer reading from the current odometer
reading.
5. Calculate fuel economy as follows:
• Standard: Divide miles traveled by gallons used.
• Metric: Multiply liters used by 100, then divide by kilometers
traveled.
Keep a record for at least one month and record the type of driving (city
or highway). This provides an accurate estimate of the vehicle's fuel
economy under current driving conditions. Additionally, keeping records
during summer and winter shows how temperature impacts fuel
economy. In general, lower temperatures mean lower fuel economy.
2013 F-650/750 (f67)
Owners Guide gf, 2nd Printing, March 2013
USA (fus)
Fuel and Refueling 119