Oldsmobile AURORA 2001 Owner's Manual page 259

If you're using fuel rated at the recommended 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 emission control
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
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vehicle may fail a smog check test. See "Malfunction
Indicator Lamp" in the Index.
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If this occurs, return to your authorized Oldsmobile
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 may contain an octane
methylcyclopentadienyl manganese tricarbonyl (MMT);
ask your service station operator whether or not the 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 may turn on.
If this occurs, return to your authorized Oldsmobile dealer
for service.
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enhancing additive called