I may be reaching that point where I am becoming educated beyond my intelligence. A diesel oil will have an overbased detergent package because of the various acids that can result as a by-product of combustion and fuel additives. Newer diesel engines have particulate filters, and require low SA oils. I am having trouble determining how you accomplish both. Looking at UOA, VOA, and PDS, I see many diesel oils still have calcium in the 3000 ppm range. Can someone explain to me, in close to english, how you keep the ash down and the base up? Is there another secret additive, a new formulation as in the new ZDDP packages, or whatever? What would be the advantage of an overbased oil in a gasoline engine. Would it be needed in an E-85 engine? Especially since most PCMO oils have a ZDDP pack of around 800 or so.