I've been wondering, are the esters used in HM oils "base oil" esters or "additive" esters? In other words, is the ester content of HM oils derived from the base oil blend (a mix of Group V and Group II), or are these esters strictly performance additives that are part of the add pack with the base oil blend being just Group II? I'm sure a base oil ester could pull double duty and be good for seals as well (which is the case with PAO-based synthetics.) Or the esters in the HM oils could just be additives. Anyone know for sure?