Ford F-250 Super Duty (1999 year). Manual — part 50

with the recommended octane rating, see your dealer or a qualified
service technician to prevent any engine damage.

Fuel quality

If you are experiencing starting, rough idle or hesitation driveability
problems during a cold start, try a different brand of “Regular” unleaded
gasoline. “Premium” unleaded gasoline is not recommended (particularly
in the United States) because it may cause these problems to become
more pronounced. If the problems persist, see your dealer or a qualified
service technician.

It should not be necessary to add any aftermarket products to your fuel
tank if you continue to use a high quality fuel.

Cleaner air

Ford approves the use of gasolines to improve air quality, including
reformulated gasolines that contain oxygenates up to 10% ethanol or
15% MTBE.

Running out of fuel

Avoid running out fuel because this situation may have an adverse affect
on powertrain components.

If you have run out of fuel:
• You may need to crank the engine several times after refueling before

the system starts to pump the fuel from the tank to the engine.

• Your “Service Engine Soon” indicator may come on. For more

information on the “Service Engine Soon” indicator, refer to the
Instrumentation chapter.

Fuel Filler Cap

Your fuel tank filler cap has an indexed design with a 1/8 turn on/off
feature.

When fueling your vehicle:

1. Turn the engine off.

2. Carefully turn the filler cap counterclockwise 1/8 of a turn until it
stops.

3. Pull to remove the cap from the fuel filler pipe.

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4. To install the cap, align the tabs on the cap with the notches on the
filler pipe.

5. Turn the filler cap clockwise 1/8 of a turn until it stops.

If the “Service Engine Soon/Check Engine” indicator comes on and stays
on when you start the engine, the fuel filler cap may not be properly
installed. Turn off the engine, remove the fuel filler cap, align the cap
properly and reinstall it.

If you must replace the fuel filler cap, replace it with a fuel filler
cap that is designed for your vehicle. The customer warranty may
be void for any damage to the fuel tank or fuel system if the
correct genuine Ford or Motorcraft fuel filler cap is not used.

The fuel system may be under pressure. If the fuel filler cap is
venting vapor or if you hear a hissing sound, wait until it stops

before completely removing the fuel filler cap. Otherwise, fuel may
spray out and injure you or others.

If you do not use the proper fuel filler cap, excessive pressure or
vacuum in the fuel tank may damage the fuel system or cause

the fuel system to work improperly in a collision, which may result in
possible personal injury.

Fuel Filter

Replace the fuel filter with an authorized Motorcraft part. The
customer warranty may be void for any damage to the fuel system
if an authorized Motorcraft fuel filter is not used.

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 fillups or fuel gauge readings are
NOT accurate as a measure of fuel economy. We do not recommend taking
fuel economy measurements during the first 1 600 km (1 000 miles) of

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driving (engine break-in period). You will get a more accurate
measurement after 3 000 km–5 000 km (2 000 miles-3 000 miles).

Filling the tank

The advertised fuel capacity of the fuel tank on your vehicle is equal to
the rated refill capacity of the fuel tank as listed in the Refill Capacities
chart in this “Owner Guide.” 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.

For consistent results when filling the fuel tank:
• Use the same filling rate setting (low — medium — high) each time

the tank is filled.

• Allow three automatic click-offs when filling.
• Always use fuel with the recommended octane rating.
• Use a known quality gasoline, preferably a national brand.
• Use the same side of the same pump and have the vehicle facing the

same direction each time you fill up.

• Have the vehicle loading and distribution the same every time.
Your results will be most accurate if your filling method is consistent.

Calculating fuel economy

1. Fill the fuel tank completely and record the initial odometer reading
(in kilometers or miles).

2. Each time you fill the tank, record the amount of fuel added (in liters
or gallons).

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.

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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.

Keep a record for at least one month and record the type of driving (city
or highway). This will provide an accurate estimate of the vehicle’s fuel
economy under current driving conditions. Additionally, keeping records
during summer and winter will show how temperature impacts fuel
economy. In general, lower temperatures give lower fuel economy.

Driving style — good driving and fuel economy habits

Give consideration to the lists that follow and you may be able to change
a number of variables and improve your fuel economy.

Habits
• Smooth, moderate operation can yield up to 10% savings in fuel.
• Steady speeds without stopping will usually give the best fuel

economy.

• Idling for long periods of time (greater than one minute) may waste

fuel.

• Anticipate stopping; slowing down may eliminate the need to stop.
• Sudden or hard accelerations may reduce fuel economy.
• Slow down gradually.
• Driving at reasonable speeds (traveling at 88 km/h [55 mph] uses 15%

less fuel than traveling at 105 km/h [65 mph]).

• Revving the engine before turning it off may reduce fuel economy.
• Using the air conditioner or defroster may reduce fuel economy.
• Using speed control (if equipped) may improve fuel economy. Speed

control can help maintain a constant speed and reduce speed changes.
You may want to turn off the speed control in hilly terrain as
unnecessary shifting between third and fourth gears may occur and
could result in reduced fuel economy.

• Warming up a vehicle on cold mornings is not required and may

reduce fuel economy.

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