Chevrolet 1997 Monte Carlo Owner's Manual page 218

Adding Equipment to the Outside of
Your Vehicle
Things you might add to the outside of your vehicle can
affect the airflow around it. This may cause wind noise
and affect windshield washer performance. Check with
your Chevrolet dealer before adding equipment to the
outside of your vehicle.
Fuel
Use regular unleaded gasoline rated at 87 octane or
higher. At a minimum, it should meet specifications
ASTM D4814 in the United States and CGSB 3.5-M93
in Canada. Improved gasoline specifications have been
developed by the American Automobile Manufacturers
Association (AAMA) for better vehicle performance
and engine protection. Gasolines meeting the AAMA
specification could provide improved driveability and
emission control system protection compared to
other gasolines.
Be sure the posted octane is at least 87. If the octane is
less than 87, you may get a heavy knocking noise when
you drive. If it's bad enough, it can damage your engine.
If you're using fuel rated at 87 octane or higher and you
hear heavy knocking, your engine needs service. But
don't worry if you hear a little pinging noise when
you're accelerating or driving up a hill. That's normal,
and you don't have to buy a higher octane fuel to get rid
of pinging. It's the heavy, constant knock that means
you have a problem.
If your vehicle is certified to meet California Emission
Standards (indicated
on
the underhood tune-up label), it
is designed to operate on fuels that meet California
specifications. If such fuels are not available in states
adopting California emissions standards, your vehicle
will operate satisfactorily on fuels meeting federal
specifications, but emission control system performance
may be affected. The malfunction indicator lamp on
your instrument panel may turn on and/or your vehicle
may fail a smog-check test. If this occurs, return to your
authorized Chevrolet dealer for diagnosis to determine
the cause of failure. In the event it is determined that the
cause of the condition is the type of fuels used, repairs
may not be covered by your warranty.
Some gasolines that are not reformulated for low
emissions contain an octane-enhancing additive called
methylcyclopentadienyl manganese tricarbonyl (MMT);
ask your service station operator whether or not his fuel
contains MMT. General Motors does not recommend the
use of such gasolines. If fuels containing MMT are used,
spark plug life may be reduced and your emission
control system performance may be affected. The
malfunction indicator lamp on your instrument panel