[RightWhale]

I have never in my life seen a barrel of oil

Don't know who this might be, but whoever it is has to have spent his life locked away in an unlighted dungeon. Possibly the only person on earth who has not seen a barrel of oil.

[Illbay]

Well, I haven't seen a barrel of oil--and neither have you.

A "barrel of oil" is simply a unit of measure. This is like saying "I've never seen an ounce of gold."

People buy and sell gold by the ounce all the time, and never actually, physically possess any of it.

This guy's been studying with Bill Clinton.