The only way to hurt gas companies is for the majority of the population to stop driving gasoline powered vehicles. My Seminar in Finance teacher might say otherwise, but I think it would leave oil producers with a large supply of crude (which as of 4/18 is already at an 8 year high) which they would have to get rid of by offering to gas stations at a lower price.

Therefore, a lower demand in gasoline powered vehicles means a lower demand in gasoline production which means a decrease in gasoline prices in the short run. After the current level of crude supply is run down and demand begins to outweigh supply, oil companies could once again charge whatever they want until the remaining gasoline buyers decide to use another type of fuel.

Of course, all of this is dependent upon there being another source of fuel to power cars, truck, planes etc. that is cheaper than gasoline is currently. Otherwise you'd end up spending more and the plan doesn't work.