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 methylcyclopentadienyl manganese tricarbonyl (MMT).
We recommend against the use of gasolines containing MMT. See Additives for additional information.
Gasoline Octane
California FuelChevrolet Cobalt Owners Manual. Engine Coolant Temperature Warning Light
This light comes on briefly
while starting the vehicle.
If it does not, have the vehicle serviced by the
dealer/retailer. If the system is working normally
the indicator light goes off.
Notice: Driving with the engine coolant temperature
warning light on could cause the vehicle to
overheat. ...