Ford 1997 Aerostar Manual page 263

Choosing the Right Fuel
Use only UNLEADED FUEL. The use of leaded
fuel is prohibited by law and could damage
your vehicle. The damage may not be covered
by your warranty.
Your vehicle was not designed to use fuel
containing manganese-based additives such as
MMT. Additionally, vehicles certified to
California emission standards (indicated on the
underhood Vehicle Emissions Control
Information label) are designed to operate on
California reformulated gasolines. If California
reformulated gasoline is not available when you
refuel, your vehicle can be operated on
non-California fuels. However, even though your
engine will perform adequately on other
gasolines, the performance of the emission
control devices and systems may be adversely
affected. Repair of damage caused by using a
fuel that your vehicle was not designed for may
not be covered by your warranty.
Octane recommendation
Your vehicle is designed to use regular gasoline
with an (R+M)/2 octane rating of 87. We do not
recommend gasolines labeled as "regular" in
high altitude areas that are sold with octane
ratings of 86 or even less.
Typical octane rating label
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