Ford Repair: Tappet Noise 1997 F-150 4.6L, tappet noise, marvel mystery oil

Question
I noticed one day a noise coming from my engine when I was outside of it and I checked the oil and nothing showed up on the dipstick so I immediately shut it off.  I changed the oil & filter and I still have the noise which I think are the tappets.  It's pretty frequent at idle. I know the previous owner was using Slick50 additive when changing the oil.  Is this a problem with 97 F-150’s or did I damage something by running it low in oil?

Answer
it is not a common problem-try running with some marvel mystery oil with your oil and see if that helps hopefully you didn't do major damage maybe it will wear out if you slightly scored a tappet.




(maybe it will wear out if you slightly scored a tappet.)
by this i mean maybe the score or rough spot will wear smooth again and work ok not that it will breakdown-