6 quarts. (once you start the motor the lines and oil filter will hold the extra Qt if it shows you put too much.)
Also, have a read of this it's important for the life of our beloved 4.0's. http://answers.yahoo.com/question/index;_ylt=AihSItuRZG9WVls8RR3I0tfty6IX;_ylv=3?qid=20090602100553AAcZDM7