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 Service & Repair Manual. Noise, Diagnosis
A visual inspection must always
be performed to confirm the presence of aftermarket components, potential
collision damage, or areas of concern.
A noise produced by a vibration
can be diagnosed in the same manner as a vibration. A noise produced by
wind, leaks, or ...