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. Accessories and Modifications
When non-dealer/non-retailer accessories are added
to the vehicle, they can affect vehicle performance
and safety, including such things as airbags, braking,
stability, ride and handling, emissions systems,
aerodynamics, durability, and electronic systems
like antilock brakes, traction control, ...