I am new to BITOG and have learned a lot by reading old posts. However, I am still very confused about "standards" in additives. I read the April '76 Popular Mechanics article provided in another thread, and I was surprised to read repeatedly in the article that in the '70s certain additives were found to be incompatible with certain synthetic bases. Specifically, zinc dithiophosphate CAUSED severe cam/lifter wear when added to an undisclosed synthetic base. In similar threads here, I have seen Terry dismiss "bad mix" conclusions (granted, sample size of one) and follow up with the conclusion that "bad mixes" do exist (Redline and M1). I assume that a "bad mix" could be either an imbalance that doesn't perform optimally, or an incompatibility in which an additive precipitates or reacts with another component. I am not concerned much about imbalances (I rarely utilize the full life span of oil anyway). However, I am concerned about incompatibilities. 1) Does anyone know what base oil was found to be incompatible with ZDP (CAS# 19210-06-1)? 2) Is "don't mix" addvice just be on the safe side or has anyone observed a repeatable, known incompatibility? 3) Could someone unintentionally create an incompatibility by making a "homebrew", combining additives, or mixing old and new oils? 4) Do standards exist that would prevent a boutique oil formulator or even a racing oil formulator from using an additive package that would be incompatible with other oils on the market? Can Mobil really know that their oil is compatible with Motul for example?