Essentials of good fuel economy
Measuring techniques
Your best source of information about actual fuel economy is you, the
driver. You must gather information as accurately and consistently as
possible. Fuel expense, frequency of fill-ups or fuel gauge readings are
NOT accurate as a measure of fuel economy. We do not recommend
taking fuel economy measurements during the first 1,000 miles
(1,600 km) of driving (engine break-in period). You will get a more
accurate measurement after 2,000–3,000 miles (3,000–5,000 km).
The advertised fuel capacity of the fuel tank(s) on your vehicle is equal
to the rated refill capacity of the fuel tank(s) as listed inFuel tanksin
this chapter. The advertised capacity is the amount of the Indicated
Capacity and the Empty Reserve combined. Indicated Capacity is the
difference in the amount of fuel in a full tank and a tank when the fuel
gauge indicates empty. Empty Reserve is the small amount of usable fuel
remaining in the fuel tank after the fuel gauge indicates empty.
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.
Note:For vehicles equipped with dual fuel tanks, engine performance
may degrade if fuel is not added to both tanks when refueling.
2008 F-650/750(f67)
Supplement
USA(fus)
Maintenance and Specifications
179
