I won't pretend to have a complete understanding of why the guy at the gas station seems to be permanently stationed out there changing the prices.  But here's how I think it goes:

Output:  Oil producing nations play a role based on the number of barrels they are willing to pump out of the ground at any given time.  Fewer barrels per day equals more money per barrel.  OPEC has a singular purpose of colluding on oil output, thereby manipulating the price they receive.

Refining Capacity:  For whatever reason that refining capacity is limited, it plays a large role in prices at the pump.  Even if the oil is delivered, shorter refining capacity still leads to shorter supply. 

Emerging economies:  Emerging economies, such as China and India, are a huge factor in the price of oil and gasoline.  Those guys who are conducting the title searches that we used to do can now afford automobiles.  So, while they drive down the price of our service, theyt are also playing a role in increasing our costs.  Can't blame them for wanting the mobility that a car offers.  We have come to depend on our mobility and so will they.  So, I don't see the trend reversing - ever.

Wall Street:  Wall Street investors take all of the above factors into account and then proceed to screw everything up based upon their expertise in everything with a price tag. 

While this is probably an overly simplistic view of the pricing of gasoline, I am but a simple person.  And I am happy to share my simple interpretation of the world economy with you.