clo,
re: "It's like diamonds (to me) a luxury, that I can live without."
Diamonds aren't rare. If we backed our money with diamonds, South Africa and deBeers Corporation would have the power to crash our currency any time they chose.
Oil would be a decent way to back a currency, except that it's all but impossible to store trillions of dollars worth of it and it has huge industrial implications. Consequently, its price would be too volatile to use it as a backing material for money.
Oil also lacks the wide recognition as being "money" that gold, silver, and (if I stretch it) even diamonds have.

Gold is $1,581/oz today. When it hits $2,000, it will be up 26.5%. Let's see how long that takes. - De 3/11/2013 - ANSWER: 7 Years, 5 Months