Ford 1998 Ranger Owner's Manual page 116

Maintenance and care
3.0L V6/4.0L V6 engine
6. Wipe the indicator clean. Insert the indicator fully, then remove it
again.
If the oil level is between the MIN and MAX marks (2.5L engine)
or between the ADD and FULL marks (3.0L and 4.0L engine)
the oil level is acceptable. DO NOT ADD OIL.
If the oil level is below the MIN
mark (2.5L engine) or ADD mark
(3.0L and 4.0L engine), add
enough oil to raise the level
within the MIN-MAX range
(2.5L engine) or the ADD-FULL
range (3.0L and 4.0L engine).
Oil levels above the MAX mark (2.5L engine) or the letter F in FULL
(3.0L and 4.0L engine) may cause engine damage. Some oil must be
removed from the engine by a service technician.
7. Put the indicator back in and ensure it is fully seated.
116
ADD 1 QT FULL