If your vehicle has the 6.0L V8 engine
(VIN Code N), use premium unleaded gasoline
with a posted octane rating of 91 or higher.
You may also use regular unleaded gasoline rated
at 87 octane or higher, but your vehicle’s
acceleration may be slightly reduced, and you
may notice a slight audible knocking noise,
commonly referred to as spark knock. If the octane
is less than 87, you may 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 might damage your
engine. 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
speci cation 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 472for additional information.
California Fuel
If your vehicle is certi ed to meet California
Emissions Standards, it is designed to operate on
fuels that meet California speci cations. 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 speci cations, but emission
control system performance may be affected. The
malfunction indicator lamp may turn on and your
vehicle may fail a smog-check test. SeeMalfunction
Indicator Lamp on page 258. If this occurs, return to
your authorized GM dealer for diagnosis. If it is
determined that the condition is caused by the type
of fuel used, repairs may not be covered by your
warranty.
471
When replacing the fuel cap, turn it clockwise until it
clicks. It will require more effort to turn the fuel cap
on the last turn as you tighten it. 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 258.
The TIGHTEN FUEL CAP message will be
displayed on the Driver Information Center (DIC) if
the fuel cap is not properly installed. SeeDIC
Warnings and Messages on page 270for 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 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. See
Malfunction Indicator Lamp on page 258.
476
