fuel GMC SIERRA 1500 2012 Owner's Guide

Black plate (32,1)GMC Sierra Owner Manual - 2012 - CRC - 11/15/11
9-32 Driving and Operating
When you are ready to drive, move
the shift lever out of P (Park) before
you release the parking brake.
If torque lock does occur, you may
need to have another vehicle push
yours a little uphill to take some of
the pressure from the parking pawl
in the transmission, then you will be
able to pull the shift lever out of
P (Park).
Shifting out of Park
This vehicle is equipped with
an electronic shift lock release
system. The shift lock release is
designed to:
.Prevent ignition key removal
unless the shift lever is in
P (Park) with the shift lever
button fully released.
.Prevent movement of the shift
lever out of P (Park), unless the
ignition is in ON/RUN or ACC/
ACCESSORY and the regular
brake pedal is applied.The shift lock release is always
functional except in the case of
an uncharged or low voltage (less
than 9 volt) battery.
If the vehicle has an uncharged
battery or a battery with low voltage,
try charging or jump starting the
battery. See
Jump Starting on
page 10‑88 for more information.
To shift out of P (Park) use the
following:
1. Apply the brake pedal.
2. Move the shift lever to the desired position.
If you still are unable to shift out of
P (Park):
1. Ease the pressure on the shift lever.
2. While holding down the brake pedal, press the shift lever all
the way into P (Park).
3. Move the shift lever to the desired position. If you are still having a problem
shifting, then have the vehicle
serviced soon.
Parking over Things
That Burn
{WARNING
Things that can burn could touch
hot exhaust parts under the
vehicle and ignite. Do not park
over papers, leaves, dry grass,
or other things that can burn.
Active Fuel Management®
Vehicles with V8 engines may
have Active Fuel Management™.
This system allows the engine to
operate on either all or half of its
cylinders, depending on the driving
conditions.

Black plate (33,1)GMC Sierra Owner Manual - 2012 - CRC - 11/15/11
Driving and Operating 9-33
When less power is required, such
as cruising at a constant vehicle
speed, the system will operate in
the half cylinder mode, allowing
the vehicle to achieve better fuel
economy. When greater power
demands are required, such as
accelerating from a stop, passing,
or merging onto a freeway, the
system will maintain full-cylinder
operation.
If the vehicle has an Active Fuel
Management™indicator, seeDriver
Information Center (DIC) on
page 5‑30 for more information on
using this display.Engine Exhaust
{WARNING
Engine exhaust contains carbon
monoxide (CO) which cannot be
seen or smelled. Exposure to CO
can cause unconsciousness and
even death.
Exhaust may enter the vehicle if:
.The vehicle idles in areas
with poor ventilation (parking
garages, tunnels, deep snow
that may block underbody
airflow or tail pipes).
.The exhaust smells or
sounds strange or different.
.The exhaust system leaks
due to corrosion or damage.
.The vehicle exhaust system
has been modified, damaged
or improperly repaired.
(Continued)
WARNING (Continued)
.There are holes or openings
in the vehicle body from
damage or aftermarket
modifications that are not
completely sealed.
If unusual fumes are detected or
if it is suspected that exhaust is
coming into the vehicle:
.Drive it only with the windows
completely down.
.Have the vehicle repaired
immediately.
Never park the vehicle with the
engine running in an enclosed
area such as a garage or a
building that has no fresh air
ventilation.

Black plate (36,1)GMC Sierra Owner Manual - 2012 - CRC - 11/15/11
9-36 Driving and Operating
{WARNING
If you have Four-Wheel Drive, the
vehicle will be free to roll—even
if the shift lever is in P (Park) —if
the transfer case is in Neutral. So,
be sure the transfer case is in a
drive gear, Two-Wheel Drive High
or Four-Wheel Drive High or
Four-Wheel Drive Low —not in
Neutral. See Shifting Into Park on
page 9‑30.
R (Reverse): Use this gear to
back up.
Notice: Shifting to R (Reverse)
while the vehicle is moving
forward could damage the
transmission. The repairs would
not be covered by the vehicle
warranty. Shift to R (Reverse) only
after the vehicle is stopped.
To rock the vehicle back and forth to
get out of snow, ice, or sand without
damaging the transmission, see If
the Vehicle Is Stuck on page 9‑15. N (Neutral):
In this position, the
engine does not connect with the
wheels. To restart when you are
already moving, use N (Neutral)
only. Also, use N (Neutral) when the
vehicle is being towed.
{WARNING
Shifting into a drive gear while the
engine is running at high speed is
dangerous. Unless your foot is
firmly on the brake pedal, the
vehicle could move very rapidly.
You could lose control and hit
people or objects. Do not shift
into a drive gear while the engine
is running at high speed.
Notice: Shifting out of P (Park)
or N (Neutral) with the engine
running at high speed may
damage the transmission. The
repairs would not be covered by
the vehicle warranty. Be sure the
engine is not running at high
speed when shifting the vehicle. D (Drive):
This position is for
normal driving. It provides the best
fuel economy. If you need more
power for passing, and you are:
.Going less than about 55 km/h
(35 mph), push the accelerator
pedal about halfway down.
.Going about 55 km/h (35 mph) or
more, push the accelerator all
the way down.
By doing this, the vehicle shifts
down to the next gear and has
more power.
D (Drive) can be used when towing
a trailer, carrying a heavy load,
driving on steep hills, or for off-road
driving. You might want to shift
the transmission to a lower gear
selection if the transmission shifts
too often.
Downshifting the transmission in
slippery road conditions could result
in skidding. See “Skidding”under
Loss of Control on page 9‑5.

Black plate (43,1)GMC Sierra Owner Manual - 2012 - CRC - 11/15/11
Driving and Operating 9-43
WARNING (Continued)
before placing the transfer case in
N (Neutral). SeeParking Brake on
page 9‑54.
N (Neutral): Shift to this setting
only when the vehicle needs to be
towed. See Recreational Vehicle
Towing on page 10‑93 orTowing the
Vehicle on page 10‑93.
2
m(Two-Wheel Drive High): This
setting is used for driving in most
street and highway situations.
The front axle is not engaged in
two-wheel drive. This setting also
provides the best fuel economy.
4
m(Four-Wheel Drive High): Use
this setting when you need extra
traction, such as on snowy or icy
roads or in most off-road situations.
This setting also engages the front
axle to help drive your vehicle. This
is the best setting to use when
plowing snow. You can shift from Two-Wheel
Drive High to Four-Wheel Drive
High or Four-Wheel Drive High to
Two-Wheel Drive High while the
vehicle is moving. In extremely cold
weather, it may be necessary to
stop or slow the vehicle to shift into
Four-Wheel Drive High.
When Using the Manual
Transfer Case
.Shifts into or out of Four-Wheel
Drive Low or N (Neutral) should
be made using quick motions to
avoid excessive gear grinding.
Shifting slowly may make it more
difficult to shift.
.You may notice that it is harder
to shift when the vehicle is cold.
After the vehicle warms up the
shifting will return to normal.
.While in Four-Wheel High or
Four-Wheel Drive Low you
may experience reduced fuel
economy.
.Avoid driving in Four-Wheel
Drive on clean, dry pavement.
It may cause your tires to wear
faster, make the transfer case
harder to shift, and run noisier.
.If the transfer case shifter is in
the N (Neutral) position and you
have difficulty reaching the
selected transfer case mode,
with the engine running, shift the
transmission momentarily to
D (Drive) and then back to
N (Neutral). This will realign the
gear teeth in the transfer case
and allow you to complete the
shift.
Shifting from Two-Wheel Drive
High to Four-Wheel Drive High
.Shifts between Two-Wheel Drive
High and Four-Wheel Drive High
can be made at any vehicle
speed.
.Shift the transfer case lever in
one continuous motion into
either the Four-Wheel Drive
High or Two-Wheel Drive High
position.

Black plate (45,1)GMC Sierra Owner Manual - 2012 - CRC - 11/15/11
Driving and Operating 9-45
Shift the transfer case in one
continuous motion into or out of the
N (Neutral) position.
Electronic Transfer Case
The transfer case knob is located
next to the steering column.
Use the dial to shift into and out of
four-wheel drive.
Recommended Transfer Case Settings
Driving ConditionsTransfer Case Settings
2m 4m4n N
Normal YES Severe YES
Extreme YES
Vehicle in Tow* YES
*See Recreational Vehicle Towing on page 10‑93 orTowing the Vehicle on
page 10‑93.
You can choose among four driving
settings:
Indicator lights in the dial show
which setting you are in. The
indicator lights will come on briefly
when you turn on the ignition and
one will stay on. If the lights do not
come on, you should take the
vehicle to your dealer for service.
An indicator light flashes while
shifting the transfer case and
remains illuminated when the shift is complete. If for some reason the
transfer case cannot make a
requested shift, it will return to the
last chosen setting.
2
m(Two-Wheel Drive High):
This
setting is used for driving in most
street and highway situations.
The front axle is not engaged in
Two-Wheel Drive. This setting also
provides the best fuel economy.

Black plate (49,1)GMC Sierra Owner Manual - 2012 - CRC - 11/15/11
Driving and Operating 9-49
Automatic Transfer Case
The transfer case knob is located
next to the steering column.
Use the dial to shift into and out of
Four-Wheel Drive.
You can choose among five driving
settings:
Indicator lights in the dial show
which setting you are in. The
indicator lights will come on briefly
when you turn on the ignition andone will stay on. If the lights do
not come on, you should take the
vehicle to your dealer for service.
An indicator light will flash while
shifting the transfer case. It will
remain illuminated when the shift is
complete. If for some reason the
transfer case cannot make a
requested shift, it will return to the
last chosen setting.
2
m(Two-Wheel Drive High):
This
setting is used for driving in most
street and highway situations.
The front axle is not engaged in
Two-Wheel Drive. This setting also
provides the best fuel economy.
AUTO (Automatic Four-Wheel
Drive): This setting is ideal for
use when road surface traction
conditions are variable. When
driving the vehicle in AUTO, the
front axle is engaged, but the
vehicle's power is sent only to the front and rear wheels automatically
based on driving conditions. Driving
in this mode results in slightly lower
fuel economy than Two-Wheel
Drive High.
4
m(Four-Wheel Drive High):
Use
the Four-Wheel Drive High position
when extra traction is needed, such
as on snowy or icy roads or in most
off-road situations. This setting also
engages the front axle to help drive
the vehicle. This is the best setting
to use when plowing snow.
4
n(Four-Wheel Drive Low): This
setting also engages the front axle
and delivers extra torque. You may
never need this setting. It sends
maximum power to all four wheels.
You might choose Four-Wheel Drive
Low if you are driving off-road in
deep sand, deep mud, deep snow,
and while climbing or descending
steep hills.

Black plate (68,1)GMC Sierra Owner Manual - 2012 - CRC - 11/15/11
9-68 Driving and Operating
Fuel
For diesel engine vehicles, see
“Fuel for Diesel Engines”in the
Duramax Diesel Supplement.
For Vehicles with gasoline engines,
please read this.
Gasoline
Use of the recommended fuel
is an important part of the proper
maintenance of this vehicle. To help
keep the engine clean and maintain
optimum vehicle performance, we
recommend the use of gasoline
advertised as TOP TIER Detergent
Gasoline.
Look for the TOP TIER label on the
fuel pump to ensure gasoline meets
enhanced detergency standards
developed by auto companies. A list
of marketers providing TOP TIER
Detergent Gasoline can be found at
www.toptiergas.com.
The eighth digit of the Vehicle
Identification Number (VIN) shows
the code letter or number that
identifies the vehicle's engine.
The VIN is at the top left of the
instrument panel. See Vehicle
Identification Number (VIN) on
page 12‑1.
Vehicles that have a FlexFuel badge
and a yellow fuel cap can use either
unleaded gasoline or ethanol fuel
containing up to 85% ethanol (E85). See
Fuel E85 (85% Ethanol) on
page 9‑71. For all other vehicles,
use only the unleaded gasoline
described under Recommended
Fuel on page 9‑68.
Recommended Fuel
For all vehicles except those with
the 6.2L V8 engine (VIN Code 2),
use regular unleaded gasoline with
a posted octane rating of 87 or
higher. If the octane rating is less
than 87, an audible knocking noise,
commonly referred to as spark
knock, might be heard when driving.
If this occurs, use a gasoline rated
at 87 octane or higher as soon as
possible. If heavy knocking is heard
when using gasoline rated at
87 octane or higher, the engine
needs service.

Black plate (69,1)GMC Sierra Owner Manual - 2012 - CRC - 11/15/11
Driving and Operating 9-69
If the vehicle has the 6.2L V8 engine
(VIN Code 2), use premium
unleaded gasoline with a posted
octane rating of 91 or higher. You
can also use regular unleaded
gasoline rated at 87 octane or
higher, but the vehicle's acceleration
could be slightly reduced, and a
slight audible knocking noise,
commonly referred to as spark
knock, might be heard. If the octane
is less than 87, you might notice a
heavy knocking noise when you
drive. If this occurs, use a gasoline
rated at 87 octane or higher as soon
as possible. Otherwise, you could
damage the engine. If heavy
knocking is heard when using
gasoline rated at 87 octane or
higher, the engine needs service.Gasoline Specifications
(U.S. and Canada Only)
At a minimum, gasoline should
meet ASTM specification D 4814
in the United States or
CAN/CGSB‐3.5 or 3.511 in
Canada. Some gasolines contain
an octane-enhancing additive called
methylcyclopentadienyl manganese
tricarbonyl (MMT). We recommend
against the use of gasolines
containing MMT. SeeFuel Additives
on page 9‑70 for additional
information.
California Fuel
Requirements
If the vehicle is certified to meet
California Emissions Standards, it is
designed to operate on fuels that
meet California specifications. See
the underhood emission control
label. If this fuel is not available in
states adopting California Emissions
Standards, the vehicle will operate
satisfactorily on fuels meeting
federal specifications, but emission control system performance might
be affected. The malfunction
indicator lamp could turn on and the
vehicle might fail a smog‐check test.
See
Malfunction Indicator Lamp on
page 5‑22. If this occurs, return to
your authorized dealer for diagnosis.
If it is determined that the condition
is caused by the type of fuel used,
repairs might not be covered by the
vehicle warranty.
Fuels in Foreign
Countries
Never use leaded gasoline or any
other fuel not recommended in the
previous text on fuel. Costly repairs
caused by use of improper fuel
would not be covered by the vehicle
warranty.
To check the fuel availability, ask an
auto club, or contact a major oil
company that does business in the
country where you will be driving.

Black plate (70,1)GMC Sierra Owner Manual - 2012 - CRC - 11/15/11
9-70 Driving and Operating
Fuel Additives
To provide cleaner air, all gasolines
in the United States are now
required to contain additives that
help prevent engine and fuel system
deposits from forming, allowing the
emission control system to work
properly. In most cases, nothing
should have to be added to the 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
and avoid problems due to dirty
injectors or valves, look for gasoline
that is advertised as TOP TIER
Detergent Gasoline. Look for the
TOP TIER label on the fuel pump to
ensure gasoline meets enhanced
detergency standards developed by
the auto companies. A list of
marketers providing TOP TIER
Detergent Gasoline can be found at
www.toptiergas.com.For customers who do not use TOP
TIER Detergent Gasoline regularly,
one bottle of GM Fuel System
Treatment PLUS, added to the fuel
tank at every engine oil change,
can help clean deposits from fuel
injectors and intake valves. GM Fuel
System Treatment PLUS is the only
gasoline additive recommended by
General Motors. It is available at
your dealer.
Gasolines containing oxygenates,
such as ethers and ethanol, and
reformulated gasolines might be
available in your area. We
recommend that you use these
gasolines, if they comply with the
specifications described earlier.
However, E85 (85% ethanol) and
other fuels containing more than
15% ethanol must not be used in
vehicles that were not designed for
those fuels.
Notice:
This vehicle was not
designed for fuel that contains
methanol. Do not use fuel
containing methanol. It can
corrode metal parts in the fuel
system and also damage plastic
and rubber parts. That damage
would not be covered under the
vehicle warranty.
Some gasolines that are
not reformulated for low
emissions can contain an
octane-enhancing additive called
methylcyclopentadienyl manganese
tricarbonyl (MMT); ask the attendant
where you buy gasoline whether the
fuel contains MMT. We recommend
against the use of such gasolines.
Fuels containing MMT can reduce
spark plug life and affect emission
control system performance. The
malfunction indicator lamp might
turn on. If this occurs, return to your
dealer for service.

Black plate (71,1)GMC Sierra Owner Manual - 2012 - CRC - 11/15/11
Driving and Operating 9-71
Fuel E85 (85% Ethanol)
Vehicles that have a FlexFuel badge
and a yellow fuel cap can use either
unleaded gasoline or ethanol fuel
containing up to 85% ethanol (E85).
For all other vehicles, use only the
unleaded gasoline described under
Recommended Fuel on page 9‑68.
We encourage the use of E85 in
vehicles that are designed to use it.
The ethanol in E85 is a“renewable”
fuel, meaning it is made from
renewable sources such as corn
and other crops.
Many service stations will not
have an 85% ethanol fuel (E85)
pump available. The U.S.
Department of Energy has
an alternative fuels website
(www.afdc.energy.gov/afdc/locator/
stations/) that can help you find
E85 fuel. Those stations that do
have E85 should have a label
indicating ethanol content. Do not
use the fuel if the ethanol content is
greater than 85%. At a minimum, E85 should meet
ASTM Specification D 5798 or
CGSB Specification 3.512. Filling
the tank with fuel mixtures that
do not meet ASTM or CGSB
specifications can affect driveability
and could cause the malfunction
indicator lamp to come on. As the
outside temperature approaches
freezing, ethanol fuel distributors
should supply winter grade ethanol,
the same as with unleaded
gasoline.
It is best not to alternate repeatedly
between gasoline and E85. If you
do switch fuels, it is recommended
that you add as much fuel as
possible
—do not add less than
11 L (3 gal) when refueling. You
should drive the vehicle immediately
after refueling for at least 11 km
(7 mi) to allow the vehicle to
adapt to the change in ethanol
concentration. E85 has less energy per liter
(gallon) than gasoline, so you will
need to refill the fuel tank more
often when using E85 than when
you are using gasoline. See
Filling
the Tank on page 9‑72.
Notice: Some additives are not
compatible with E85 fuel and can
harm the vehicle's fuel system.
Do not add anything to E85.
Damage caused by additives
would not be covered by the
vehicle warranty.
Notice: This vehicle was not
designed for fuel that contains
methanol. Do not use fuel
containing methanol. It can
corrode metal parts in the fuel
system and also damage plastic
and rubber parts. That damage
would not be covered under the
vehicle warranty.