GMC 2005 Sierra 1500 Pickup, Owner'S Manual, Page: 400 / 574

Adding Equipment to the Outside
of Your Vehicle
Things you might add to the outside of your vehicle can
affect the airflow around it. This may cause wind
noise and affect windshield washer performance. Check
with your dealer before adding equipment to the
outside of your vehicle.
Fuel
If your vehicle has a diesel engine, see “Diesel Fuel
Requirements and Fuel System” in the Diesel Engine
Supplement.
For vehicles with gasoline engines, please read this.
Gasoline Octane
For all except vehicles with the 6000 V8 (VIN Code N)
engine, use regular unleaded gasoline with a posted
octane of 87 or higher. If the octane is less than 87, you
may get 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. A little pinging noise when you accelerate or drive
uphill is considered normal. This does not indicate a
problem exists or that a higher-octane fuel is necessary.
If you are using 87 octane or higher-octane fuel and hear
heavy knocking, your engine needs service.
If you have the 6000 V8 (VIN Code N) engine, use
premium unleaded gasoline with a posted octane of
91 or higher for best performance. You may also
use middle grade or regular unleaded gasoline rated at
87 octane or higher, but your vehicle’s acceleration
may be slightly reduced. If the octane is less than 87,
you may get a heavy knocking noise when you drive.
If this occurs, use gasoline rated at 87 octane or higher
as soon as possible. Otherwise, you might damage
your engine.
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