Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSCADILLAC1991FLEETWOOD FWD V8-300 4.9LREPAIR AND DIAGNOSISSPECIFICATIONSFLUID TYPE SPECIFICATIONSFUEL
1991 Cadillac Fleetwood FWD V8-300 4.9L
Fuel
1991 Cadillac Fleetwood FWD V8-300 4.9LSECTION Fuel
***UPDATED BY TSB T-92-16 DATED OCTOBER 1991
ALCOHOL FUEL TYPES:
Methyl Tertiary-Butyl Ether (MTBE):
Fuel containing Methyl Tertiary-butyl Ether (MTBE) may be used, providing there is no more than 15% alcohol by volume.
Ethanol:
Fuel containing ethanol (ethyl) or grain alcohol may be used, providing there is no more than 10% ethanol alcohol by volume.
Methanol:
Fuel containing methanol (methyl) or wood alcohol may be used, providing there is no more than 5% methanol by volume. Use of fuel (gasohol) that contains more than 5% methanol can corrode metal fuel system components and damage plastic and rubber parts.
GASOLINE:
Premium 91 octane Unleaded gasoline must be used.
In some areas premium unleaded fuel (minimum of 91 octane) may not be available. To allow the vehicles to operate with regular unleaded fuel the base ignition timing must be retarded from 10° to 6° BTDC. Retarding the initial timing will have a small adverse effect on composite fuel economy and performance.
Retarding timing for use with regular unleaded fuel has no effect on:
^ Durability
^ Engine cooling
^ Idle stability
Vehicles should be returned to proper timing when premium unleaded fuel becomes available.
RENDER: 1.0x
NO RELATED
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.