syn·thet·ic
[sin-thet-ik]
adjective
1.of, pertaining to, proceeding by, or involving synthesis ( opposed to
analytic ).
2.
noting or pertaining to compounds formed through a chemical process by human agency, as opposed to those of natural origin:
Rotella T5 is clearly a
real synthetic oil, since it is the product of a chemical process by human agency applied to an oil source of otherwise natural origin.
Many synthetic oils are made by cracking the molecules of mineral oil. Those that manufacture oils from different sources (cough, AMSOIL) try to discount the "synthetic" claims because the source was, in fact, oil to begin with. We are dealing with semantics here and it doesn't make a damn bit of difference in the end. You could synthesize your motor oil from cake frosting and whale sperm (if that were possible) and it would be no more or less
"synthetic" than Rotella T5. The only important thing in it is, what are the properties of the end product. How well does it perform under various conditions for the application at hand. Not how
synthetic it happens to be.
Now don't get me started on "natural" foods claims...