Someone please explain

Okay, I know I have already had an blog entry concerning gasoline prices, but this morning I became extremely frustrated when I noticed that the price of gasoline had gone up six cents over night at the local station. What occurred overnight to warrant such an increase? I ask because I don't know. I went to my source for all things unknown, the internet, to see if I could find an answer. But alas I did not. I found many sites, many articles, and much information concerning crude oil and gas futures, supply and demand, macro and micro economics, refining capacity, and even politics and conspiracy. BUT, NOTHING about the cause of the daily change in gas prices. The tanker truck delivers gas to the station and it is put in tanks underground. Now, unless there is a delivery every day, the gas in the ground increases in value as the price goes up daily, as much as six cents a gallon as it did overnight. WTF? I really need an explanation. Of course with my limited readership I know I won't get an answer here and will just continue to be frustrated. But on the outside chance that someone does know, or knows where to look, I would really appreciate an answer.