Nice thought but the problem is that oil is a global fungible commodity.
Even if you found a source guaranteeing they were supplied with domestic oil, you are contributing to global demand and the global price of oil. To the Saudis it doesn't matter much where your oil is sourced from -- just that you're buying it.
ding, ding, ding, ding ... we have a winner
Don Pardo, tell Uncledave what he's won for understanding how commodity markets actually work