The basics of supply and demand, even in a market as curated as global petroleum is, are fairly easy to understand. Today's example: southern California, where some stations are beginning to run out of gas due to "refinery supply problems" at both Chevron and Mobil, reports USA Today. The result? Prices could hit $5-a-gallon soon. AAA says that the average in California today is $4.486 a gallon, well above the national average of $3.789 and making a run on the $4.61 record from June 2008.

Since some gas stations are no longer buying wholesale fuel, the tanks are running dry. USA Today notes that a Costco in Simi Valley started selling premium (which was available) at regular prices (since that fuel was not available). Another station owner told Bloomberg, "I can get gas, but it's going to cost me $4.90 a gallon, and I can't sell it here for $5. ... My market is open, but no gas." He can't sell it for $5 today, but with California prices jumping 20 cents overnight and 40 cents for the week, that could change soon. In fact, a station in Calabasas was selling gas for $5.69 yesterday, along with signs that said: "We are sorry, it is not our fault."