It is cheaper for the oil companies to buy the 113 octane ethanol and then blend it with the lower octane gas to bring it up to 87 octane so they can sell it. The other alternative is to spend more time refining the crude oil up to 87 octane gas. They are making more money by speeding up the process and producing more gas in a day because they don't have to refine it as long to get to the octane ratings.