It's confusing as hell , come say zinc or zddp is not needed after cam is broken in itherssay always needed , I always add a bottle of ZDDP , but never used a high zinc oil . Found this on RP site , guess Ill buy some XPR 10 40 and skip the zinc .
"" Yes. All Royal Purple engine oils contain the zinc/phosphorus compound zinc dialkyl dithiophosphate (ZDDP). Royal Purple HPS and XPR lines of engine oils are formulated with a higher concentration of these elements and are suitable for both roller and flat tappet valve trains.""
