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 WarningInstallation Procedure
Cut the front compartment upper side rail in corresponding locations to
fit the remaining original panel. The sectioning joint should
be trimmed to allow a gap of one-and-one-half-times the metal thickness at
the sectioning joint.
Create a 50 mm (2 in) backing plate from the unused ...
Heating and Air Conditioning System Description and Operation
Engine Coolant
Engine coolant is the key element of the heating system. The thermostat
controls engine operating coolant temperature. The thermostat
also creates a restriction for the cooling system that promotes a positive
coolant flow and helps prevent cavitation. Coolant enters the
heater ...
OnStar Additional Information
Transferring Service
Press to request account transfer
eligibility information. The Advisor can assist in canceling or removing account
information. If OnStar receives information that vehicle ownership has changed,
OnStar may send a voice message to the vehicle, requesting updated account i ...