GMC 1993 Jimmy Owner's Manual page 271

I f you're using fuel rated at
91 octane or higher and you still hear heavy
knocking, your engine needs service. But don't worry i f 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
10% ethanol is fine for your vehicle.
Methanol is methyl or wood alcohol.
.
Gasolines for Cleaner Air
Your use of gasoline with detergent 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 materials called 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 so, 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
detergents and oxygenates, and if they have been reformulated to reduce
vehicle emissions.
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