Gasoline Octane
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 your vehicle’s acceleration could be
slightly reduced, and you might notice a slight
audible knocking noise, commonly referred to as
spark knock. 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 you are using gasoline rated
at 87 octane or higher and you hear heavy
knocking, the 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 357for 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 234. 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.
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