i guess because as said above the oil molecules are smaller a little bit of it is gettting burned off, just a guess dont know for sure, but i have heard that for the duratec's it is not uncommon for it to loose a little oil over a period of time, and that the engine is perfectly fine in it

98.5 Black SE ATX S&B filter, SVT MAF, optimized SVT TB, mesh grille, removed orange reflectors, painted rear reflector, gutted pre-cats, optimized SVT LIM, 19lb injectors, resonator removed cant afford an svt but lookin for 1 in nc