Temporarily shifting supply and demand is not the answer. If everyone bought their oil from one company forcing other companies to lower prices to compete consumers could manipulate the market. If certain refineries were not processing oil because of competitors were selling more then they too would be affected.
If everyone bought only Pennsylvania grade crude then the off- shore companies would be forced to lower prices to gain back a market share. When there is only a price difference of 3 or 4 cents per gallon there is little incentive to buy exclusively from one supplier.
The oil companies control refinery output to keep supply low and blame demand and the consumers for high prices. Look at the price of diesel which was once the lower price fuel. My nephew runs his diesel Liberty on self processed cooking oil since new. Much cleaner burning and better on the engine. Also, naturally sulpher free!