Unable to Connect to OnStar Message
If there is limited cellular coverage
or the cellular network has reached
maximum capacity, this message
may come on. Push 
to try the
call again or try again after driving a
few miles into another cellular area.
See also:
Engine Oil Additives/Engine Oil Flushes
Do not add anything to the oil.
The recommended oils with the dexos specification and displaying the dexos
certification mark are all that is needed for good performance and engine
protection.
...
Roadside Service (Mexico)
As a new owner, your vehicle is automatically enrolled in the Roadside
Assistance program.
The services are available at no cost under the terms and conditions of the
program. The Roadside Assist ...
Gasoline Specifications (U.S. and Canada Only)
At a minimum, gasoline should meet ASTM specification D 4814 in the United
States or CAN/CGSB—3.5 or 3.511 in Canada. Some gasolines contain an
octane-enhancing additive called methylcyclopentadieny ...