I found it interesting that Mobile1 lists a shelf life on it’s web site, however Valvoline has no shelf life listed for any of it’s products, per it’s web site, so they believe like most us us that is will always be good. In their Q&A they even say so.
Not all synthetic oil uses a mineral oil base:
“Pure synthetic oils (polyalkyleneglycol) are
the types used almost exclusively within the industrial sector in polyglycol oils for heavily
loaded gearboxes. These are typically concocted by even more intelligent blokes in even whiter lab coats. These chaps break apart the molecules that make up a variety of substances, like vegetable and animal oils,
and then recombine the individual atoms that make up those molecules to build new, synthetic molecules. This process allows the chemists to actually "fine tune" the molecules
as they build them. Clever stuff. But Polyglycols don't mix with normal mineral oils.”
Car Bibles : The Engine Oil Bible
It has been awhile since I have looked at “oil” and a discussion on "expiration" on a truck Web site lead me to more searches.