Pontiac 1993 Grand Am Owner's Manual page 201

Service & Appearance Care
Fuel
(CONT.:)
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
txoblem.
2.3L High Output Quad 4 Engine
(Code A):
The 8th digit of your Vehicle
Identification Number (VIN) shows the
code letter for your engine. You will
find the VIN at the top left of your
instrument panel. (See the Index under
Rhicle ldentijication Number.)
Use premium unleaded gasoline rated at
91 octane or higher. You may use middle
grade or regular unleaded gasolines, but
your vehicle may not accelerate as well.
The gasoline you use should meet
specifications ASTM D4814 in the U.S.
and CGSB 3.5-92 in Canada. These
fuels should have the proper additives,
so you should not have to add anything
to the fuel.
In the U.S. and Canada, it's easy to be
sure you get the right kind of gasoline
(unleaded). You'll see "UNLEADED"
right on the pump. And only unleaded
nozzles will
fit
into your vehicle's filler
neck.
Be sure the posted octane for premium
is at least 91 (at least 89 for middle
grade and 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.
8 8 8
a00