Put in 5w-20 or the lifters will rattle.If you put in the wrong oil in Fords,the lifters will rattle.I have heard of this happening in Fords,one guy brought one in because the lifters were rattling and it was the wrong grade oil.Luckily the guy bought this one from another person whom put an extended warranty on it, a superduty truck with the V10 and it was covered under warranty