For service and parts needs, visit your dealer. You will receive genuine GM parts and GM-trained and supported service people.
Genuine GM parts have one of these marks:

Vehicle Care
California Proposition
65 WarningFuel (Gasoline)
GM recommends the use of TOP
TIER detergent gasoline to keep the
engine cleaner and reduce engine
deposits. See www.toptiergas.com
for a list of TOP TIER detergent
gasoline marketers and applicable
countries.
Do not use any fuel labeled E85 or
FlexFuel. Do not use gasoline with
ethanol ...