Buick 2000 Regal Owner's Manual page 247

If you have the 3800 Supercharged V6 engine
(VIN Code 1), use premium unleaded gasoline rated
at 91 octane or higher. With the 3800 Supercharged
engine, in an emergency, you may be able to use a lower
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octane as low as 87 if heavy knocking does not
occur. If you are using 91 or higher octane unleaded
gasoline and you hear heavy knocking, your engine
needs service.
It is recommended that the gasoline meet specifications
which have been developed by the American Automobile
Manufacturers Association (AAMA) and endorsed by
the Canadian Motor Vehicle Manufacturers Association
for better vehicle performance and engine protection.
Gasolines meeting the AAMA specification could
provide improved driveability and emission control
system performance compared to other gasolines.
Be sure the posted octane for premium is at least 91
(at least 87 for regular). 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.
6-4
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.) If this occurs, return to
your authorized Buick 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
called 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 Buick dealer for service.
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enhancing additive