I have a 1984 Ford Econoline 150 with the 4.9 300 engine. I checked my oil this morning after been running for about 10 minutes at the most, because I heard a slight knocking sound from the engine. When I pulled the dipstick, it was bone dry! It took like 3 1/2 qts to get it just below the add mark, but my oil gauge says I'm getting good pressure and It don't burn oil, because it never smokes, and I haven't ever seen any leaking.. What do ya'll think is going on? Thanks!