Blue, did you read the article?
Here are a couple reasons/answers from the article:

'Gasoline, meanwhile, has become pricier at the pump because refiners have been producing less of it. Profits from refining have been so thin over the last several months that refiners have been earning little, or even losing money, on producing gasoline.

So now they are storing oil or selling it to traders, or retooling their refineries to produce less gasoline and more products with better profit margins, like heating oil, diesel or jet fuel.

Valero has curtailed gasoline supplies by extending maintenance time at some refineries and cutting production at eight of its 16 refineries. “There is not a lot of incentive right now to produce gasoline because there is lots of it,” said Bill Day, a spokesman for Valero, the nation’s largest refiner. “Obviously it would be better for us if there were more stability in prices.” '