It doesn't matter if they dump 1000 million gallons of oil on the market. There are still a limit on the number of refineries. They are (supposedly) all max capacity, and can't produce anymore gasoline no matter the amount of oil dumped on the market.
Or that is one of the many oil company excuses. Which go hand in hand with no new one's being built in 30 years, and "no one wants them in their backyard".
