
GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-11349177) - 2018 - CRC - 10/17/17
244 Driving and Operating
After Off-Road Driving
Remove any brush or debris that
has collected on the underbody or
chassis, or under the hood. These
accumulations can be a fire hazard.
After operation in mud or sand,
have the brake linings cleaned and
checked. These substances can
cause glazing and uneven braking.
Check the body structure, driveline,
steering, suspension, wheels, tires,
and exhaust system for damage and
check the fuel lines and cooling
system for any leakage.
More frequent maintenance service
is required. See theMaintenance
Schedule 0448.
Driving on Wet Roads
Rain and wet roads can reduce
vehicle traction and affect your
ability to stop and accelerate.
Always drive slower in these types
of driving conditions and avoid
driving through large puddles and
deep-standing or flowing water.
{Warning
Wet brakes can cause crashes.
They might not work as well in a
quick stop and could cause
pulling to one side. You could
lose control of the vehicle.
After driving through a large
puddle of water or a car/vehicle
wash, lightly apply the brake
pedal until the brakes work
normally.
Flowing or rushing water creates
strong forces. Driving through
flowing water could cause the
vehicle to be carried away. If this
happens, you and other vehicle
occupants could drown. Do not
ignore police warnings and be
very cautious about trying to drive
through flowing water.
Hydroplaning
Hydroplaning is dangerous. Water
can build up under the vehicle's
tires so they actually ride on the
water. This can happen if the road is
wet enough and you are going fast
enough. When the vehicle is
hydroplaning, it has little or no
contact with the road.
There is no hard and fast rule about
hydroplaning. The best advice is to
slow down when the road is wet.
Other Rainy Weather Tips
Besides slowing down, other wet
weather driving tips include:
.
Allow extra following distance.
. Pass with caution.
. Keep windshield wiping
equipment in good shape.
. Keep the windshield washer fluid
reservoir filled.
. Have good tires with proper
tread depth. See Tires0389.
. Turn off cruise control.

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-11349177) - 2018 - CRC - 10/17/17
300 Driving and Operating
Caution (Continued)
.Fuel with a posted octane
rating of less than the
recommended fuel. Using
this fuel will lower fuel
economy and performance,
and may decrease the life of
the emissions catalyst.
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 may be
affected. The malfunction indicator
lamp could turn on and the vehicle
may not pass a smog-check test.
See Malfunction Indicator Lamp
(Check Engine Light) 0150. 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 may not be covered by the
vehicle warranty.
Fuels in Foreign
Countries
The U.S., Canada, and Mexico post
fuel octane ratings in anti-knock
index (AKI). For fuel not to use in a
foreign country, see
“Prohibited
Fuels” inFuel 0299.
Fuel Additives
To keep fuel systems clean, TOP
TIER detergent gasoline is
recommended. See Fuel0299.
If TOP TIER detergent gasoline is
not available, one bottle of GM Fuel
System Treatment Cleaner added to
the fuel tank at every engine oil
change, can help. GM Fuel System
Treatment Cleaner is the only
gasoline additive recommended by
General Motors. It is available at
your dealer. If your vehicle is able to use E85 or
FlexFuel, GM Fuel System
Treatment Cleaner - FlexFuel is the
only recommended additive for use.
Do not use any other additives with
an E85 or FlexFuel vehicle. See
E85 or FlexFuel
0300.
E85 or FlexFuel
Vehicles with a yellow sticker on the
fuel door can use either unleaded
gasoline or fuel containing up to
85% ethanol (E85). All other
vehicles should use only the
unleaded gasoline as described in
Fuel 0299.
The use of E85 or FlexFuel is
encouraged when the vehicle is
designed to use it. E85 or FlexFuel
is made from renewable sources.
To help locate fuel stations that
carry E85 or FlexFuel, the U.S.
Department of Energy has an
alternative fuels website. See
www.afdc.energy.gov/afdc/locator/
stations.

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-11349177) - 2018 - CRC - 10/17/17
Vehicle Care 395
would mean that the tire's
sidewall is 75 percent as high as
it is wide.
(4) Construction Code
:A letter
code is used to indicate the type
of ply construction in the tire.
The letter R means radial ply
construction; the letter D means
diagonal or bias ply
construction; and the letter B
means belted-bias ply
construction.
(5) Rim Diameter
:Diameter of
the wheel in inches.
(6) Load Range
:Load Range.
(7) Service Description
:The
service description indicates the
load index and speed rating of a
tire. If two numbers are given as
in the example, 120/116, then
this represents the load index for
single versus dual wheel usage
(single/dual). The speed rating is
the maximum speed a tire is
certified to carry a load.
Tire Terminology and
Definitions
Air Pressure:The amount of
air inside the tire pressing
outward on each square inch of
the tire. Air pressure is
expressed in kPa (kilopascal)
or psi (pounds per square inch).
Accessory Weight
:The
combined weight of optional
accessories. Some examples of
optional accessories are
automatic transmission, power
windows, power seats, and air
conditioning.
Aspect Ratio
:The relationship
of a tire's height to its width.
Belt
:A rubber coated layer of
cords between the plies and the
tread. Cords may be made from
steel or other reinforcing
materials. Bead
:The tire bead contains
steel wires wrapped by steel
cords that hold the tire onto
the rim.
Bias Ply Tire
:A pneumatic tire
in which the plies are laid at
alternate angles less than
90 degrees to the centerline of
the tread.
Cold Tire Pressure
:The
amount of air pressure in a tire,
measured in kPa (kilopascal)
or psi (pounds per square inch)
before a tire has built up heat
from driving. See Tire Pressure
0 397.
Curb Weight
:The weight of a
motor vehicle with standard and
optional equipment including the
maximum capacity of fuel, oil,
and coolant, but without
passengers and cargo.
DOT Markings
:A code molded
into the sidewall of a tire
signifying that the tire is in
compliance with the U.S.

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-11349177) - 2018 - CRC - 10/17/17
398 Vehicle Care
Caution
Neither tire underinflation nor
overinflation is good.
Underinflated tires, or tires
that do not have enough air,
can result in:
.Tire overloading and
overheating which could
lead to a blowout.
.Premature or
irregular wear.
.Poor handling.
.Reduced fuel economy.
Overinflated tires, or tires that
have too much air, can
result in:
.Unusual wear.
.Poor handling.
.Rough ride.
.Needless damage from
road hazards. The Tire and Loading
Information label on the vehicle
indicates the original equipment
tires and the correct cold tire
inflation pressures. The
recommended pressure is the
minimum air pressure needed to
support the vehicle's maximum
load carrying capacity.
For additional information
regarding how much weight the
vehicle can carry, and an
example of the Tire and Loading
Information label, see
Vehicle
Load Limits 0248. How the
vehicle is loaded affects vehicle
handling and ride comfort. Never
load the vehicle with more
weight than it was designed to
carry.
When to Check
Check the tires once a month
or more. Do not forget the spare tire,
if the vehicle has one. See
Full-Size Spare Tire
0425 for
additional information.
How to Check
Use a good quality pocket-type
gauge to check tire pressure.
Proper tire inflation cannot be
determined by looking at the tire.
Check the tire inflation pressure
when the tires are cold, meaning
the vehicle has not been driven
for at least three hours or no
more than 1.6 km (1 mi).
Remove the valve cap from the
tire valve stem. Press the tire
gauge firmly onto the valve to
get a pressure measurement.
If the cold tire inflation pressure
matches the recommended
pressure on the Tire and
Loading Information label, no
further adjustment is necessary.
If the inflation pressure is low,
add air until the recommended
pressure is reached. If the

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-11349177) - 2018 - CRC - 10/17/17
Customer Information 469
GM Mobility
Reimbursement Program
This program is available to
qualified applicants for cost
reimbursement, up to certain limits,
of eligible aftermarket adaptive
equipment required for the vehicle,
such as hand controls or a
wheelchair/scooter lift for the
vehicle.
To learn about the GM Mobility
program, see www.gmmobility.com
or call the GM Mobility Assistance
Center at 1-800-323-9935. Text
Telephone (TTY) users, call
1-800-833-9935.
General Motors of Canada also has
a Mobility program. See www.gm.ca
or call 1-800-GM-DRIVE
(800-463-7483) for details. TTY
users call 1-800-263-3830.
Roadside Assistance
Program
For U.S.-purchased vehicles, call
1-888-881-3302; (Text Telephone
(TTY): 1-888-889-2438).
For Canadian-purchased vehicles,
call 1-800-268-6800.
Service is available 24 hours a day,
365 days a year.
Calling for Assistance
When calling Roadside Assistance,
have the following information
ready:
.Your name, home address, and
home telephone number
. Telephone number of your
location
. Location of the vehicle
. Model, year, color, and license
plate number of the vehicle
. Odometer reading, Vehicle
Identification Number (VIN), and
delivery date of the vehicle
. Description of the problem
Coverage
Services are provided for the
duration of the vehicle's powertrain
warranty.
In the U.S., anyone driving the
vehicle is covered. In Canada, a
person driving the vehicle without
permission from the owner is not
covered.
Roadside Assistance is not a part of
the New Vehicle Limited Warranty.
General Motors North America and
GMC reserve the right to make any
changes or discontinue the
Roadside Assistance program at
any time without notification.
General Motors North America and
GMC reserve the right to limit
services or payment to an owner or
driver if they decide the claims are
made too often, or the same type of
claim is made many times.
Services Provided
.Emergency Fuel Delivery:
Delivery of enough fuel for the
vehicle to get to the nearest
service station.

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-11349177) - 2018 - CRC - 10/17/17
484 OnStar
3. Say the entire number withoutpausing, including a “1”and the
area code. System responds:
“OK, calling.”
Calling 911 Emergency
1. Press=. System responds:
“OnStar ready.”
2. Say “Call.”System responds:
“Call. Please say the name or
number to call.”
3. Say “911”without pausing.
System responds: “911.”
4. Say “Call.”System responds:
“OK, dialing 911.”
Retrieve My Number
1. Press=. System responds:
“OnStar ready.”
2. Say “My number.” System
responds: “Your OnStar
Hands-Free Calling number is,”
then says the number.
End a Call
Press=. System responds: “Call
ended.”
Verify Minutes and Expiration
Press=and say “Minutes” then
“Verify” to check how many minutes
remain and their expiration date.
Diagnostics
By monitoring and reporting on the
vehicle’s key systems, OnStar
Advanced Diagnostics provides a
way to keep up on maintenance.
Capabilities vary by model. See
www.onstar.com for details and
system limitations. Message and
data rates may apply.
Includes:
. Diagnostic Alerts: Set
preferences to receive real-time
e-mails, texts, or monthly
reports of the vehicle’s health.
Or press
Qto have an Advisor
initiate a remote diagnostic
report. .
Proactive Alerts: Receive a
real-time e-mail or text message
regarding potential issues with
key vehicle components, such
as the battery, fuel system,
or starter system. Alerts for
potential issues appear on the
infotainment display. Proactive
Alerts are designed to help
predict specific types of issues
based on information collected
from the vehicle. Other factors
may affect vehicle performance.
Not all issues will deliver alerts.
In some cases, a dealer service
check may be required to
confirm the accuracy of the
alerts.
. Dealer Maintenance Notification:
Have the vehicle notify your
preferred dealer when it is time
for maintenance. Your dealer will
then contact you to set up an
appointment.
To begin, pressQto speak to an
Advisor, or see www.onstar.com.