Lincoln 1997 Town Car Owner's Manual page 244

Typical octane rating label
Do not be concerned if your vehicle sometimes
knocks lightly. However, if it knocks heavily under
most driving conditions on the recommended
octane fuel, see your dealer or a qualified service
technician to prevent any engine damage.
Fuel quality
If you are experiencing starting, rough idle or
hesitation problems try a different brand of fuel. If
the condition persists, see your dealer or a qualified
service technician.
242
The American Automobile Manufacturers
Association (AAMA) issued a gasoline specification
to provide information on high quality fuels that
optimize the performance of your vehicle. We
recommend the use of gasolines that meet the
AAMA specification if they are available.
It should not be necessary to add any aftermarket
products to your fuel tank if you continue to use a
high-quality fuel.
Cleaner Air
Ford approves the use of gasolines to improve air
quality, including reformulated gasolines that contain
oxygenates such as a maximum of 10% ethanol or
15% MTBE. There should be no more than 5%
methanol with cosolvents and additives to protect
the fuel system.