Pontiac 1993 Sunbird Owner's Manual page 150

If you're using fuel rated at 87 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
(oxygenates), such as MTBE or
alcohol?
MTBE is "methyl tertiary-butyl ether."
Fuel that is no more than 15% MTBE is
fine for your vehide.
Ethanol is ethyl or grain alcohol.
Properly-blended fuel that is no more
than 10% ethanol is fine for your
vehicle.
Methanol is methyl or wood alcohol.
NOTICE:
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.
Gasolines for Cleaner Air
Your use of gasoline with deposit
control additives will help prevent
deposits from forming in your engine
and fuel system. That helps keep your
engine in tune and your emission
control system working properly. It's
good for your vehicle, and you'll be
doing your part for cleaner air.
Many gasolines are now blended with
oxygenates. General Motors
recommends that you use gasolines
with these blending materials, such as
MTBE and ethanol. By doing so, you
can help clean the air, especially in
those parts of the country that have
high carbon monoxide levels.
. ,
In addition, some gasoline suppliers are
now producing reformulated gasolines.
These gasolines are specially designed
to reduce vehicle emissions. General
Motors recommends that you use
reformulated gasoline. By doing go, you
can help clean the air, especially in
those parts of the country that have
high ozone levels.
You should ask your service station
operators if their gasolines contain
deposit control additives and
oxygenates, and if they have beep
reformulated to reduce vehicle
;
emissions.
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