I have a 1999 super cab f150 4x4 with the 5.4L. I have the same problem I've heard atleast in my year the v8's have a tendency to leak oil at the head gasket but no oil in the water. I realy dont know what to tell you but if you at the min line its maybe a quart and a half to two quarts my 5.4L holds 6.5 quarts yours should hold 6 to 6.5 quarts