"We" didn't establish any such thing. A few self-proclaimed and vociferous "experts"
-grandly- pronounced that the shelf life of finished motor oil is five years with nothing but their own Kentucky windage, or advice from un-named sources, to back their opinion. As usual, the wanna-be expert sheep chimed in with unquestioned agreement, and, thus, a Standard was born... I've made it a point to look up the MSDSs of any brand oil I might be even remotely intrigued by (when available online per blender) and, without exception, they all list that the products are stable -indefinitely- when stored sealed at normal ambient temperatures, and furthermore do not undergo destructive auto-polymerization. I figure, rightly or wrongly, since the oil companies, themselves, are responsible for performing the federally mandated tests as to their petroleum products' chemical stability, their published data should be taken as definitive. MSDS reports are where the rubber meets the road, guys - everything else is either advertising or anecdotal. An MSDS report does not tell you everything about a finished motor oil, but what it does tell you, is gospel unless the company wants to have its A$$ hauled into federal district court. On that basis, I'll make my own grand pronouncement that, when stored sealed, motor oil will remain viably usable in new vehicles until at least the next released API service category, and remain usable indefinitely in vehicles that originally called for their particular, or earlier, API service category. ATFs are probably likewise stable.
[ December 19, 2003, 10:17 PM: Message edited by: Ray H ]