I have a 6.4 SRT 8 in my 2011 ram and the lifters (new mopar ones for a 2011 5.7 I bought years ago) sounded horrible, almost like a rod was about to come out the side some time and others they would be pretty quiet, I was about to yank it all back down and try some "hellcat" lifters (they are all the same ones now) and the guy at the dodge dealer suggested to drain it and run 5w40 mobile 1 synthetic (I had tried a bunch of other weights and brands) and by golly I have put another 20,000 miles on the truck since switching to that and never a tick out of any of them.