Gold is extracted and usually refined locally, perhaps it is exported as an alloy with Silver or Platinum or other metal. After more refinement it can be converted to gold bars.
Oil has more variety, it's a mix of a hundred (thousand?) similar compound and it's exported (almost?) raw. So the composition and the level of the impurities vary a lot from the different sources. You can't ignore the source of the oil because your refinery may not be able to use it.
A better comparison is gasoline. The difference of gasoline with a bar of gold is that gasoline is still a mix of somewhat similar substances, but the variation is small. There are many variants, with different octane rating and different additives. It's not 100% true, but gasoline is somewhat fungible and you don't care too much about the origin if it has the quality you are looking for.