Octane Recommendations; Octane Recommendations (5.0L V8 Engine); Fuel Quality - Ford 2012 Mustang Owner's Manual

Maintenance and Specifications
Your vehicle was not designed to use fuel or fuel additives with metallic
compounds, including manganese-based additives.
Note: Use of any fuel other than those recommended may cause
powertrain damage, a loss of vehicle performance, and repairs may not
be covered under warranty.

Octane recommendations

Your vehicle is designed to use
87
"Regular" unleaded gasoline with a
pump (R+M)/2 octane rating of 87.
Some stations offer fuels posted as
(R+M)/2 METHOD
"Regular" with an octane rating
below 87, particularly in high altitude areas. Fuels with octane levels
below 87 are not recommended.
Do not be concerned if your engine sometimes knocks lightly. However, if
it knocks heavily under most driving conditions while you are using fuel
with the recommended octane rating, see your authorized dealer to
prevent any engine damage.

Octane recommendations (5.0L V8 engine)

Your vehicle is designed to run on regular fuel with an octane rating of
87 (R+M)/2 or higher. For best overall performance, premium fuel with
an octane rating of 91 (R+M)/2 or higher is recommended.
See the Shelby GT500 Supplement for octane requirements of the
Shelby GT500.

Fuel quality

If you are experiencing starting, rough idle or hesitation driveability
problems during a cold start, try a different brand of "Regular" unleaded
gasoline.
Do not add aftermarket fuel additive products to your fuel tank. It
should not be necessary to add any aftermarket products to your fuel
tank if you continue to use high quality fuel of the recommended octane
rating. These products have not been approved for your engine and
could cause damage to the fuel system. Repairs to correct the effects of
using an aftermarket product in your fuel may not be covered by your
warranty.
Many of the world's automakers approved the World-Wide Fuel Charter
that recommends gasoline specifications to provide improved
performance and emission control system protection for your vehicle.
295
2012 05+ Mustang (197)
Owners Guide, 1st Printing
USA (fus)