A lot of 'fuss' has been made about the move to lower additive levels in oils for environmental reasons. SL capped zinc/phosphorus at 1000 ppm; SM caps it at 800; SN will leave it at that. Were there caps BEFORE SL-rated oil? Have they slowly been going down over the years, or is it only recently that the industry has focused on them? Reason I ask is if you look at a analysis of an SJ oil it has a Zn level of around 1100 ppm. If you look at the analysis of an SH-rated oil (there is one on here somewhere, can't find it now) it has a level of around 1000-1100 as well. It just seems that around the 'SG-SH-SJ era', you didn't see the clear-cut drops in additive levels like you do in the transistion of SJ-SL-SM. Anyone got info on this?