I was just thinking about the trends of the past 6 years...
The crude oil price directly reflects gasoline prices at the pump, obviously. Over the past 6 years, there were a few times when the average US price of gasoline at the pump was as high as 6% the cost of a barrel of crude oil. This was when the price of crude was very low, around 32-36$/barrel, but has happened a few other times as well. The lowest margin seems to be about 3%, when prices were high.
I think the high margin at low prices has something to do with the national average $0.45/gal in taxes included in the price (from what i understand, these are taxes that don't fluctuate... IE: its not a %?). So if the price is low, the tax cost becomes more of a % of the total price, and opposite for higher prices.
http://www.GasBuddy.com/gb_retail_pr...me=48&units=us