FORD 2001 Lincoln Town Car - Manual (Page 260)

Tonneau cover care (if equipped)
To avoid damage to the vinyl tonneau cover, do not use any silicone
based cleaner or conditioner. Do not use stiff bristle brushes or abrasive
materials or cleaners.
Hot waxes applied by commercial car washes can affect the cleanability
of vinyl material.
Using high water pressure or wand-type car washes against the vinyl
cover and tonneau frame rails may cause water leaks and possible seal
damage.
Maintenance and care
260