Possible Causes

WARNING: This page does not describe the selected car, but rather 10 other vehicles, including the 2002 Ford RV Cutaway, 2002 Ford Pickup, 2002 Ford F550 Super Duty, 2002 Ford F450 Super Duty, and 2002 Ford Excursion. However, it is still accessible from the selected car via links, so may be relevant.

Loss of lube oil pressure.
Oil level low; oil leak, oil consumption, incorrect servicing.
Oil level high; incorrect servicing, fuel dilution from tandem fuel pump, fuel dilution from injector "O" rings.
Oil contamination with coolant; oil cooler, head gasket, porosity.
Low reservoir level; engine built dry (not pressure lubed), prolonged period of not running, excessive cranking without starting.