Gasoline Octane Rating

All vehicles except Cobra are designed to use regular unleaded fuel with an octane rating of 87. At service stations, the octane rating is displayed in a label on the pumps.

• In some parts of the country, "regular" grade fuels are sold with octane ratings of 86 or even less. This is commonplace in areas of high altitude.
• It is not recommended to use such fuels.
• Always use a fuel with an octane rating of 87, even if it is sold as a "midgrade" or "premium."
• Using a fuel with a lower octane rating can cause persistent and heavy knocking, which can damage the engine.
• Do not be concerned if the vehicle sometimes knocks lightly when you drive up a hill or when accelerating. See a dealer or a qualified service technician if, when using a fuel with the specified octane rating:
  • Vehicle knocks heavily under all driving conditions
  • Vehicle knocks lightly while you drive at cruising speed on level roads.

In most cases it should not be necessary to use a "premium" grade of fuel with an octane rating of higher than 87.

If the engine experiences problems with starting, rough engine idle, or hesitation when the engine is cold, it may be caused by fuel with low volatility.

• Trying a different grade and/or brand of fuel may solve the condition. If the condition persists, see your dealer or a qualified service technician.

Cobra

The Mustang Cobra engine has been designed to operate using PREMIUM UNLEADED fuel with an octane rating of 91 or higher.

• Regular unleaded fuel with an octane rating of 87 may be used if necessary.
• For optimum performance and driveability it is recommended that you use premium unleaded fuel.

In some parts of the country, "premium" grade fuels are sold with octane ratings of less than 91.

• This is commonplace in areas of high altitude.
• It is recommended that you use only those "premium" fuels with an octane rating of 91 or higher.

Always use a fuel with an "intake system deposit control" detergent that helps keep your vehicle's intake valves clean.

• To find out if a fuel has detergents, look for advertising that the petroleum company does to promote its detergent fuels or look for signs posted near the pumps at the service station.