GMC 2003 Sierra - Manual (Page 380)

Fuel
If your vehicle has a diesel engine, see ^’Djesef Fuel
Requlrennents and Fuel SysTem" In the DIeset Engine
Supplement.
For vehicles with gasoline engines, please read this.
Gasoline Octane
Use regular unleaded gasoline wi!h a posted ociane of 87
or higher. If the octane is less than 87. you may gat a
heavy knocking noise when you driva. IMhis occurs, use
a gasoline rated al 87 oclane or higher as soon a&
possihlen Otherwise, you might daniage your engine. A
little panging noise when you accobrate or drive uphill is
considered normal. This does not iricHcgte a problem
exists or that a higher-octane fuel is necessary. It you are
using 37 octarte or highernDctane fuel and hear heavy
knocking, your engine needs service.
GasoHne Specifications
tt Is recommended that gasoline meet specilicalians
which were developed by the American Automobile
Wlanufaclurfirs Association and endorsed by the
Canadian Vehicle Manufacturers Association for belter
vehicle performance and engine prelection. Gasoline
meeling Ihese specifications could proviefe improved
driveability and emission control system performance
compared to olher gasolina.
In Canaefai look for the
“Auto Makers' Choice"
label on the pump.
Canada Only
5-5