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Engine Fan Breakage
{CAUTION:
Changing the Fan Drive Ratio or Engine
Governed Speed:
If you change the fan drive ratio or increase
the governed speed of the engine, you may
increase stress and the fan could eventually
fail. If the fan breaks apart while it is
rotating, pieces can cause severe injury to
anyone — such as a service technician — who
is nearby. And, of course, the pieces can
severely damage the vehicle. Do not change
the fan drive ratio or increase the governed
speed of the vehicle without getting the
necessary information from your dealer.
CAUTION: (Continued)
CAUTION: (Continued)
Winter Fronts, Grille Covers or Obstructions:
Winter Fronts, grille covers or other add-on
equipment causing obstructions in front or
behind the fan should not be used on this
vehicle. If this causes the fan to eventually
break apart while it is rotating, the pieces can
cause severe injury to anyone nearby, such as
a service technician working on the engine,
and of course the pieces can severely damage
the vehicle.
5-5
Page 234 of 398

Fuel
If your vehicle has a diesel engine, seeDiesel Engine
Fuel on page 5-7.
For vehicles with gasoline engines, please read this.
Gasoline Octane
Use regular unleaded gasoline with a posted octane
rating of 87 or higher. If the octane rating is less than 87,
you may notice an audible knocking noise when you
drive, commonly referred to as spark knock. If this
occurs, use a gasoline rated at 87 octane or higher as
soon as possible. If you are using gasoline rated at
87 octane or higher and you hear heavy knocking, your
engine needs service.
Gasoline Speci cations
At a minimum, gasoline should meet ASTM
specification D 4814 in the United States or
CAN/CGSB-3.5 in Canada. Some gasolines may
contain an octane-enhancing additive called
methylcyclopentadienyl manganese tricarbonyl (MMT).
General Motors recommends against the use of
gasolines containing MMT. SeeAdditives on page 5-6
for additional information.
Additives
To provide cleaner air, all gasolines in the United States
are now required to contain additives that will help
prevent engine and fuel system deposits from forming,
allowing your emission control system to work
properly. In most cases, you should not have to add
anything to your fuel. However, some gasolines contain
only the minimum amount of additive required to
meet U.S. Environmental Protection Agency regulations.
To help keep fuel injectors and intake valves clean,
or if your vehicle experiences problems due to
dirty injectors or valves, look for gasoline that is
advertised as TOP TIER Detergent Gasoline. Also, your
GM dealer has additives that will help correct and
prevent most deposit-related problems.
Gasolines containing oxygenates, such as ethers and
ethanol, and reformulated gasolines may be available in
your area. General Motors recommends that you use
these gasolines if they comply with the specifications
described earlier. However, E85 (85% ethanol)
and other fuels containing more than 10% ethanol must
not be used in vehicles that were not designed for
those fuels.
5-6
Page 235 of 398

Notice:Your vehicle was not designed for fuel that
contains methanol. Do not use fuel containing
methanol. It can corrode metal parts in your fuel
system and also damage the plastic and rubber
parts. That damage would not be covered under
your warranty.
Some gasolines that are not reformulated for low
emissions may contain an octane-enhancing additive
called methylcyclopentadienyl manganese tricarbonyl
(MMT); ask the attendant where you buy gasoline
whether the fuel contains MMT. General Motors
recommends against the use of such gasolines. Fuels
containing MMT can reduce the life of spark plugs
and the performance of the emission control system may
be affected. The malfunction indicator lamp may turn
on. If this occurs, return to your authorized GM dealer for
service.Diesel Engine Fuel
For the Caterpillar®diesel, see the Caterpillar®
Operation & Maintenance Manual for information
concerning fuel usage.
Notice:Diesel fuel or fuel additives not
recommended in this manual could damage your
fuel system and engine. Your warranty would
not cover this damage. And:
Diesel fuel that has been mixed with engine oil
or automatic transmission uid could damage
your engine and emission controls.
Aftermarket diesel fuel additives are not tested
by General Motors. Some additives, particularly
those which contain alcohol or water
emulsi ers, may damage your fuel system. If
you believe that unique circumstances call for a
fuel additive to be used, consult your dealer
for advice.
If you ever run out of diesel fuel, it can be
difficult to restart your engine. To avoid
this, never let your tank get empty.
If gasoline is ever accidentally added to the fuel
tank, to avoid severe engine damage, do not run the
engine until the fuel tank can be drained.
If you run out of fuel,Running Out of Fuel on page 5-17
tells you how to restart your engine.
5-7
Page 236 of 398

What Fuel to Use
In the United States, for best results use No. 2-D diesel
fuel year-round (above and below freezing conditions)
as oil companies blend No. 2-D fuel to address climate
differences. No. 1-D diesel fuel may be used in very
cold temperatures (when it stays below 0°F or−18°C);
however, it will produce a power and fuel economy
loss. Avoid the use of No. 1-D diesel fuel in warm or hot
climates. It may result in stalling, poor starting when
the engine is hot, and may damage the fuel injection
system.
At a minimum, the diesel fuel you use should meet the
latest version of ASTM specification D 975 (Grade
Low Sulfur) in the United States. In addition, the Engine
Manufacturers Association (EMA) has identified
properties of an improved diesel fuel for better engine
performance and durability. Diesel fuels corresponding
to the EMA Recommended Guideline on Premium
Diesel Fuel (FQP-1A) could provide better starting, less
noise, and better vehicle performance. If there are
questions about the fuel you are using, contact your fuel
supplier.
If your vehicle has the 6.6L engine, it is acceptable to
use diesel fuel containing up to 5% biodiesel (B5),
but the final blended fuel must meet the same
specification, ASTM D 975 (Grade Low Sulfur), as other
fuels used in your vehicle, and the biodiesel used for
making this fuel must meet the latest version ofASTM specification D 6751. Biodiesel is produced from
vegetable oils or animal fat that have been chemically
modified to reduce the possibility of damage to your fuel
system and engine. Higher concentration (i.e., greater
than B5) biodiesel-containing fuels or the use of
unmodified bio-oils blended into diesel fuel at any
concentration is not recommended and could damage
your fuel system and engine. Such damage would
not be covered by your warranty. If there are questions
about the biodiesel-containing fuels you are using,
contact your fuel supplier.
Diesel fuel may foam when you fill your tank. This can
cause the automatic pump nozzle to shut off, even
though your tank is not full. If this happens, just
wait for the foaming to stop and then continue to fill
your tank.
{CAUTION:
Heat coming from the engine may cause the
fuel to expand and force the fuel out of your
tank. If something ignites the fuel, a re could
start and people could be burned. To help
avoid this, ll your fuel tank only until the
automatic nozzle shuts off. Do not try to top
it off.
5-8
Page 237 of 398

What Fuel to Use in Canada
Canadian fuels are blended for seasonal changes.
Diesel Type “A” fuel is blended for better cold weather
starting (below 0°F or−18°C); however, you may
notice some power and fuel economy loss. If Type “A”
fuel is used in warmer temperatures, stalling and
hard starting may occur. Diesel Type “B” fuel is blended
for temperatures above 0°F (−18°C). The emission
control system requires the use of diesel fuel with
low-sulfur (.05% by weight) content. Both low- and
higher-sulfur fuels will be available in Canada. Only
low-sulfur diesel fuels are available in the United States.
It is important that diesel-powered trucks are refueled
only with low-sulfur fuel. Use of fuels with higher-sulfur
content will affect the function of the emission
components and may cause reduced performance,
excessive smoke, and unpleasant odor.
At a minimum, the diesel fuel you use should meet the
latest version of specification CAN/CGSB-3.517
(Low Sulfur Diesel) in Canada. In addition, the Engine
Manufacturers Association (EMA) has identified
properties of an improved diesel fuel for better engine
performance and durability (FQP-1A). Diesel fuels
corresponding to the EMA description could provide
better starting, less noise, and better vehicle
performance. If there are questions about the fuel you
are using, contact your fuel supplier.If your vehicle has the 6.6L engine, it is acceptable to
use diesel fuel containing up to 5% biodiesel (B5),
but the final blended fuel must meet the same
specification, CAN/CGSB-3.517 (Low Sulfur Diesel) in
Canada, as other fuels used in your vehicle, and
the biodiesel used for making this fuel must meet the
latest version of ASTM specification D 6751. Biodiesel is
produced from vegetable oils or animal fat that have
been chemically modified to reduce the possibility
of damage to your fuel system and engine. Higher
concentration (i.e., greater than B5) biodiesel-containing
fuels or the use of unmodified bio-oils blended into
diesel fuel at any concentration is not recommended and
could damage your fuel system and engine. Such
damage would not be covered by your warranty. If there
are questions about the biodiesel-containing fuels you
are using, contact your fuel supplier.
5-9
Page 238 of 398

Very Cold Weather Operation
Follow the instructions listed previously under the
heading “What Fuel to Use.”
Notice:Never use home heating oil or gasoline in
your diesel engine. They can cause engine
damage.
In cold weather, your fuel filter may become clogged
(waxed). To unclog it, move the vehicle to a warm
garage area and warm the filter to between 32°F and
50°F (0°C to 10°C). You will not need to replace it.
Additional information on the fuel filter follows.
Water in Fuel
{CAUTION:
Diesel fuel containing water is still ammable.
You could be burned. If you ever try to drain
water from your fuel, keep sparks, ames and
smoking materials away from the mixture.Notice:If there is water in your diesel fuel and the
weather is warm or humid, fungus and bacteria
can grow in the fuel. They can damage your
fuel system. A diesel fuel biocide can be used to
sterilize your fuel system. However, your fuel system
may still need to be cleaned. Your dealer can
advise you of the appropriate solution.
If your fuel tank needs to be purged to remove
water, see your dealer or a quali ed technician.
Improper purging can damage your fuel system.
Sometimes, water can be pumped into your fuel
tank along with your diesel fuel. This can happen if a
service station does not regularly inspect and clean
its fuel tanks, or if it gets contaminated fuel from
its suppliers.
If this happens, the
water-in-fuel light, if
equipped, will come on in
the instrument panel. If it
does, the water must be
drained. Your dealer can
show you how to do this.
If the light comes on, use this chart to determine what
action to take.
5-10
Page 239 of 398

Water In Fuel Light
Problem Recommended Action
Light comes on
intermittently.Drain water from the
fuel filter.
Light stays on at
temperatures above
freezing.Drain the fuel filter
immediately. If no water
can be drained and the
light stays on, see your
dealer for assistance.
Light stays on at
temperatures below
freezing.Drain the fuel filter
immediately. If no water
can be drained, water
may be frozen in the
water drain system, or in
the fuel lines. Move the
vehicle to a warm location
to thaw out, and then
drain the filter system.
Light stays on
immediately after
refueling, and a large
amount of water was
possibly pumped into the
fuel tank.Fuel tank purging is
required. See your dealer
for assistance.Notice:If you drive when this warning indicator is
on, you can damage your fuel injection system
and your engine. If the indicator comes on right after
you refuel, it means water was pumped into your
fuel tank. Turn off your engine immediately.
Then, have the water drained at once.
To drain water, do the following:
1. Stop and park the vehicle in a safe place. Turn off
the engine and apply the parking brake.
2. Remove the fuel cap.
3. Place a fuel-resistant container under the fuel filter.
The filter drain valve is located on the bottom of the
fuel filter.
If your vehicle has the 6.6L engine, the fuel filter is
located in the engine compartment on the driver’s
side of the vehicle. If your vehicle has either
the 7.2L or 7.8L engine, the fuel filters are located
in the engine compartment on the driver’s side
of the vehicle, and on the driver’s side frame rail in
front of the fuel tank.
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Page 240 of 398
4. Open the drain valve
by turning two to
three turns. When fuel
empties from the
valve, all the water has
been drained. Close
the valve hand-tight.
5. Remove the fuel-resistant container and properly
dispose of the contaminated fuel. To find out how
to properly dispose of contaminated diesel fuel, see
Engine Oil (Caterpillar
®Diesel Engine) on
page 5-24orEngine Oil (DURAMAX®Diesel) on
page 5-24orEngine Oil (Gasoline Engine) on
page 5-28.6. Install the fuel cap.
7. Start the engine and let it run for a few minutes. If the
engine stalls, the fuel system may need to be primed.
While draining the water from the fuel filter, air may
enter the fuel system. If air has entered the fuel
system the fuel system will need to be primed.
If the water-in-fuel light comes on again after driving a
short distance or the engine runs rough or stalls, a large
amount of water has probably been pumped into the
fuel tank. The fuel tank should be purged.
5-12