Pontiac 1993 Grand Am Owner's Manual page 202

If you're using fuel rated at 91 octane or
higher and you still 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.
What about gasoline with blending
materials that contain oxygen, such as
MTBE or alcohol?
MTBE is "methyl tertiary-butyl
ether? Fuel that is no more than 15 %
MTBE is fine for your vehicle.
Ethanol is ethyl or grain alcohol.
Properly-blended fuel that is no more
than 1 0 % ethanol is fine for your
vehicle.
Methanol is methyl or wood alcohol.
I
Fuel that is more than 5 %
methanol is bad for your vehicle.
Don't use it. It can corrode metal
parts in your fuel system and also
damage plastic and rubber parts.
That damage wouldn't be covered
under your warranty. And even at
5 % or less, there must be
:
. .
.''cosolvents" and corrosion
'
'preventers in this fuel to help avoid
these problems.
Fuel Capacity:
15.2 U.S. Gallons
(57.5L). Use
unleaded fuel only.
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