I just did an oil change on my 2001 F250 5.4 4x4 over the weekend. After dumping the old oil back into the 5 quart container, I noticed that I was down 3 quarts of oil. The truck doesn't smoke and I don't see any leaks anywhere. It just hit 100k miles. I noticed other times when checking the dipstick, it reads low. Does the 5.4 have oil returns that can be possibly clogged and keeping the oil in the valve covers???
How many miles between changes? Ford considers consumption of a quart every 1000 to 1500 miles normal. I've had three 5.4L engines over the past decade and they all consumed oil to some degree. Switching to synthetic seemed to help.