Your motor should be fine. 4 quarts out of 6 is ok. It is alittle low, but not too bad. Keep checking the level on a regular basis. You may wanna change your PVC valve. If it is clogged, it will increase oil comsumption. Don't ask me how. Some people on here ALOT smarter than me may cime in here.
My 2003 behaves the same way . I put 6 qts. in (and add at least 1 qt during the 3k oil change period ) and take out 4-4.5 qts when changing the oil . Also my dip stick is not accurate , it shows half-full mark with 6 qts oil (which is Ford recommendation by the owner's manual).
Ford manual says "do not add if oil level is within the marks" . But at the absence of an accurate dipstick , it is a challenge (even if you re-mark your dipstick for your own "new full mark " . There is always a question about the accurate 5 qts level.
If you did not change your own oil , you would not have a clue about how much oil is coming out . So, relax , you are not alone.
I wish I could have the answer for the minimum oil level required for proper lubrication . Let me see what I need for that ;
A full scale lab , at least 100 v-10 triton engines ( for testing variety of engine oil formulations & levels ) , possibly a dozen technicians and few engineers . Also some precision testing equipment needed to monitor wear properties on numerous engine components . It could get real expensive very quickly , unless we get it published by the engine manufacturer .
Mine burns about 1qt every 1000 miles or so as well and from what i have read on here its seems common/normal. I normally add half a qt at a time when it gets close to the minimum mark on the dip stick but after reading your guys posts maybe i will stop doing that lol.