I Have a 5.4 v8 05 f250 with 120,000 miles. I drove truck one day and then did not drive truck for about a week. I started truck and I lost oil pressure so I changed oil out and oil pressure was perfect, about 10 miles I lost pressure and engine started to malfunction so i turned truck off asap! Started truck again and pressure was fine so I turned around to take truck back home and just when I pulled in driveway pressure left again. Any thouhts would be greatly appreciated!