bountyh: This topic has been discussed to death. Between every other week to every month someone comes on BITOG and starts a thread like this. Long story short: The advice they are giving you is genuine. It will drive you crazy just trying to figure out what "synthetic" is. The industry has been developing over a century, there are so many processes to use and any number of variations on each of those processes, it's hard to draw the line. "man-made" is not the answer. Almost every motor oil (including synthetic!) is derived from either crude oil, hydrocarbon gas of some type, or some oil-to-gas process in order to assemble "designer molecules." It's better to look at the oils overall performance than its constituent parts. Keep in mind that most times, you can't even find out the process used. The vast majority of motor oil companies don't tell you. Assembling a definitive list of Group II, Group III (Hydro-cracked [Synthetic in the US]), Group IV (PAO), and Group V (Ester) oils will be darn near impossible. Knock yourself out trying.
I'll give you a leg up: Royal Purple uses Group V, AMSOIL uses Group IV (mostly), Schaeffer uses HC and PAO, and Pennzoil seems to only use Group III now, as does Valvoline. Can the average engine tell the difference? Probably not.
As for ZDP/ZDDP the UOA/VOA section has information on zinc for just about every oil out there. But keep in mind that doesn't always reflect the exact content. Newer oils have been reformulated with other anti-wear additives (moly, some of the newer calcium compounds that also increase TBN) and some are rumored to use organic additives, which don't always show up well on a cheap $25 oil analysis.
