gas type GMC ENVOY 2008 Owner's Manual

In any particular crash, no one can say whether an
airbag should have inated simply because of the
damage to a vehicle or because of what the repair
costs were. For frontal airbags, ination is determined
by what the vehicle hits, the angle of the impact,
and how quickly the vehicle slows down. For roof-rail
airbags, deployment is determined by the location
and severity of the side impact. In a rollover event,
roof-rail airbag deployment is determined by the
direction of the roll.
What Makes an Airbag Inate?
In a deployment event, the sensing system sends
an electrical signal triggering a release of gas from
the inator. Gas from the inator lls the airbag causing
the bag to break out of the cover and deploy. The
inator, the airbag, and related hardware are all part
of the airbag module.
Frontal airbag modules are located inside the steering
wheel and instrument panel. For vehicles with roof-rail
airbags, there are airbag modules in the ceiling of the
vehicle, near the side windows that have occupant
seating positions.
How Does an Airbag Restrain?
In moderate to severe frontal or near frontal collisions,
even belted occupants can contact the steering wheel
or the instrument panel. In moderate to severe side
collisions, even belted occupants can contact the inside
of the vehicle.
Airbags supplement the protection provided by safety
belts. Frontal airbags distribute the force of the impact
more evenly over the occupant’s upper body, stopping
the occupant more gradually. Roof-rail airbags distribute
the force of the impact more evenly over the occupant’s
upper body.
Rollover capable roof-rail airbags are designed to
help contain the head and chest of occupants in the
outboard seating positions in the rst and second rows.
The rollover capable roof-rail airbags are designed to
help reduce the risk of full or partial ejection in rollover
events, although no system can prevent all such
ejections.
But airbags would not help in many types of collisions,
primarily because the occupant’s motion is not toward
those airbags. SeeWhen Should an Airbag Inflate? on
page 1-58for more information.
Airbags should never be regarded as anything more
than a supplement to safety belts.
1-59

Gasoline Octane
Use regular unleaded gasoline with a posted octane
rating of 87 or higher. If the octane rating is less than 87,
you might 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, the
engine needs service.
Gasoline Specications
At a minimum, gasoline should meet ASTM specication
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. SeeAdditives on page 5-7for
additional information.
California Fuel
If your vehicle is certied to meet California Emissions
Standards, it is designed to operate on fuels that meet
California specications. See the underhood emission
control label. If this fuel is not available in states adopting
California emissions standards, your vehicle will operate
satisfactorily on fuels meeting federal specications, but
emission control system performance might be affected.
The malfunction indicator lamp could turn on and your
vehicle might fail a smog-check test. SeeMalfunction
Indicator Lamp on page 3-41. If this occurs, return to your
authorized dealer/retailer for diagnosis. If it is determined
that the condition is caused by the type of fuel used,
repairs might not be covered by your warranty.
5-6

{CAUTION:
Fuel can spray out on you if you open the fuel
cap too quickly. If you spill fuel and then
something ignites it, you could be badly
burned. This spray can happen if your tank is
nearly full, and is more likely in hot weather.
Open the fuel cap slowly and wait for any hiss
noise to stop. Then unscrew the cap all the way.
Be careful not to spill fuel. Do not top off or overll the
tank and wait a few seconds after you have nished
pumping before removing the nozzle. Clean fuel from
painted surfaces as soon as possible. SeeWashing Your
Vehicle on page 5-103.
When replacing the fuel cap, turn it clockwise until it
clicks. Make sure the cap is fully installed. The
diagnostic system can determine if the fuel cap has been
left off or improperly installed. This would allow fuel to
evaporate into the atmosphere. SeeMalfunction Indicator
Lamp on page 3-41.There may also be a light that comes on in the
instrument panel to let you know if your gas cap is not
properly installed. SeeCheck Gas Cap Light on
page 3-49for more information.
{CAUTION:
If a re starts while you are refueling, do not
remove the nozzle. Shut off the ow of fuel by
shutting off the pump or by notifying the
station attendant. Leave the area immediately.
Notice:If you need a new fuel cap, be sure to get
the right type. Your dealer/retailer can get one
for you. If you get the wrong type, it may not t
properly. This may cause your malfunction indicator
lamp to light and may damage your fuel tank and
emissions system. SeeMalfunction Indicator Lamp
on page 3-41.
5-9

What to Use
To determine what kind of lubricant to use, see
Recommended Fluids and Lubricants on page 6-12.
Headlamp Aiming
Headlamp aim has been preset at the factory and
should need no further adjustment.
However, if your vehicle is damaged in a crash, the
headlamp aim may be affected. Aim adjustment to the
low-beam headlamps may be necessary if oncoming
drivers ash their high-beam headlamps at you
(for vertical aim).
If the headlamps need to be re-aimed, it is
recommended that you take the vehicle to your
dealer/retailer for service.
Bulb Replacement
For the proper type of replacement bulbs, see
Replacement Bulbs on page 5-54.
For any bulb changing procedure not listed in this
section, contact your dealer/retailer.
Halogen Bulbs
{CAUTION:
Halogen bulbs have pressurized gas inside
and can burst if you drop or scratch the bulb.
You or others could be injured. Be sure to read
and follow the instructions on the bulb
package.
5-49