I've used Marvel mystery oil... I like that stuff.. My engine was what i call clanking, but could be called tapping pretty loud if you put your head near the fender by the front tires... It started after used 5-40 rotella t5 oil... It didn't go away tho... i tried Marvel mystery oil per what a old mechanic said and within 50 miles the noise went away... I haven't used it since but it deff didn't hurt my engine... It did thin the oil a little tho and i could hear the lifters/rockers tapping more..
2013 6.2 V8 Camaro SS 3,000 miles :-)
1998 5.9 V8 Limited Platinum ZJ 151,xxx miles
1998 4.0 I6 Laredo ZJ 207,xxx miles Yay !