just got an 08 f150 5.4 used with 20,000 miles. as far as i can tell it has been on MC blend its whole life judging by the dealer motorcraft oci sticker when i got it and mc filter. from what i read about fords i should keep the mc filter but what would be the best quality oil for my truck from a parts store, and what interval should i go? and another thing when should i flush or drain and fill the trans?